diff --git a/Makefile b/Makefile
index 06bf064306..c0b9d90d42 100644
--- a/Makefile
+++ b/Makefile
@@ -29,7 +29,7 @@ all: lib
 USER_CFLAGS=$(strip $(shell test -f perf-cppflags && cat perf-cppflags))
 
 # If the user doesn't specify an -O setting, we default to -O3, except
-# for upb_def which gets -Os.
+# for def which gets -Os.
 ifeq (, $(findstring -O, $(USER_CFLAGS)))
   USER_CFLAGS += -O3
   DEF_OPT = -Os
@@ -39,9 +39,9 @@ endif
 CC=gcc
 CXX=g++
 CFLAGS=-std=gnu99
-INCLUDE=-Isrc -Itests -I.
+INCLUDE=-Itests -I.
 CPPFLAGS=$(INCLUDE) -Wall -Wextra $(USER_CFLAGS)
-LDLIBS=-lpthread src/libupb.a
+LDLIBS=-lpthread upb/libupb.a
 
 # Build with "make Q=" to see all commands that are being executed.
 Q=@
@@ -60,7 +60,7 @@ endif
 # different -D options, which can include different header files.
 deps: gen-deps.sh Makefile $(CORE) $(STREAM)
 	$(Q) CPPFLAGS="$(CPPFLAGS)" ./gen-deps.sh $(CORE) $(STREAM)
-	$(E) Regenerating dependencies for src/...
+	$(E) Regenerating dependencies for upb/...
 
 $(ALLSRC): perf-cppflags
 
@@ -71,25 +71,23 @@ $(ALLSRC): perf-cppflags
 
 # The core library.
 CORE= \
-  src/upb.c \
-  src/upb_handlers.c \
-  src/upb_descriptor.c \
-  src/upb_table.c \
-  src/upb_def.c \
-  src/upb_msg.c \
-  src/upb_varint.c \
-
-
-# Common encoders/decoders -- you're almost certain to want these.
-STREAM= \
-  src/upb_decoder.c \
-  src/upb_stdio.c \
-  src/upb_textprinter.c \
-  src/upb_strstream.c \
-  src/upb_glue.c \
+  upb/upb.c \
+  upb/handlers.c \
+  upb/descriptor.c \
+  upb/table.c \
+  upb/def.c \
+  upb/msg.c \
+  upb/bytestream.c \
+
+# Library for the protocol buffer format (both text and binary).
+PB= \
+  upb/pb/decoder.c \
+  upb/pb/varint.c \
+  upb/pb/glue.c \
+  upb/pb/textprinter.c \
 
 # Parts of core that are yet to be converted.
-OTHERSRC=src/upb_encoder.c
+OTHERSRC=upb/pb/encoder.c
 
 BENCHMARKS_SRC= \
   benchmarks/main.c \
@@ -114,13 +112,13 @@ ALLSRC=$(CORE) $(STREAM) $(BENCHMARKS_SRC) $(TESTS_SRC)
 clean_leave_profile:
 	rm -rf $(LIBUPB) $(LIBUPB_PIC)
 	rm -rf $(call rwildcard,,*.o) $(call rwildcard,,*.lo) $(call rwildcard,,*.dSYM)
-	rm -rf src/upb_decoder_x86.h
+	rm -rf upb/pb/decoder_x86.h
 	rm -rf benchmark/google_messages.proto.pb benchmark/google_messages.pb.* benchmarks/b.* benchmarks/*.pb*
-	rm -rf src/jit_debug_elf_file.o
-	rm -rf src/jit_debug_elf_file.h
+	rm -rf upb/pb/jit_debug_elf_file.o
+	rm -rf upb/pb/jit_debug_elf_file.h
 	rm -rf $(TESTS) tests/t.*
-	rm -rf src/descriptor.pb
-	rm -rf src/upbc deps
+	rm -rf upb/descriptor.pb
+	rm -rf tools/upbc deps
 	rm -rf lang_ext/lua/upb.so
 	cd lang_ext/python && python setup.py clean --all
 
@@ -128,9 +126,9 @@ clean: clean_leave_profile
 	rm -rf $(call rwildcard,,*.gcno) $(call rwildcard,,*.gcda)
 
 # Core library (libupb.a).
-SRC=$(CORE) $(STREAM)
-LIBUPB=src/libupb.a
-LIBUPB_PIC=src/libupb_pic.a
+SRC=$(CORE) $(PB)
+LIBUPB=upb/libupb.a
+LIBUPB_PIC=upb/libupb_pic.a
 lib: $(LIBUPB)
 
 
@@ -138,7 +136,7 @@ OBJ=$(patsubst %.c,%.o,$(SRC))
 PICOBJ=$(patsubst %.c,%.lo,$(SRC))
 
 ifneq (, $(findstring DUPB_USE_JIT_X64, $(USER_CFLAGS)))
-src/upb_decoder.o: src/upb_decoder_x86.h
+upb/pb/decoder.o: upb/pb/decoder_x86.h
   ifeq (, $(findstring DNDEBUG, $(USER_CFLAGS)))
   $(error "JIT only works with -DNDEBUG enabled!")
   endif
@@ -158,29 +156,29 @@ $(LIBUPB_PIC): $(PICOBJ)
 	$(E) 'CC -fPIC' $<
 	$(Q) $(CC) $(CFLAGS) $(CPPFLAGS) -c -o $@ $< -fPIC
 
-# Override the optimization level for upb_def.o, because it is not in the
+# Override the optimization level for def.o, because it is not in the
 # critical path but gets very large when -O3 is used.
-src/upb_def.o: src/upb_def.c
+upb/def.o: upb/def.c
 	$(E) CC $<
 	$(Q) $(CC) $(CFLAGS) $(CPPFLAGS) $(DEF_OPT) -c -o $@ $<
 
-src/upb_def.lo: src/upb_def.c
+upb/def.lo: upb/def.c
 	$(E) 'CC -fPIC' $<
 	$(Q) $(CC) $(CFLAGS) $(CPPFLAGS) $(DEF_OPT) -c -o $@ $< -fPIC
 
-src/upb_decoder_x86.h: src/upb_decoder_x86.dasc
+upb/pb/decoder_x86.h: upb/pb/decoder_x86.dasc
 	$(E) DYNASM $<
-	$(Q) lua dynasm/dynasm.lua src/upb_decoder_x86.dasc > src/upb_decoder_x86.h
+	$(Q) lua dynasm/dynasm.lua upb/pb/decoder_x86.dasc > upb/pb/decoder_x86.h
 
 ifneq ($(shell uname), Darwin)
-src/jit_debug_elf_file.o: src/jit_debug_elf_file.s
+upb/pb/jit_debug_elf_file.o: upb/pb/jit_debug_elf_file.s
 	$(E) GAS $<
-	$(Q) gcc -c src/jit_debug_elf_file.s -o src/jit_debug_elf_file.o
+	$(Q) gcc -c upb/pb/jit_debug_elf_file.s -o upb/pb/jit_debug_elf_file.o
 
-src/jit_debug_elf_file.h: src/jit_debug_elf_file.o
+upb/pb/jit_debug_elf_file.h: upb/pb/jit_debug_elf_file.o
 	$(E) XXD $<
-	$(Q) xxd -i src/jit_debug_elf_file.o > src/jit_debug_elf_file.h
-src/upb_decoder_x86.h: src/jit_debug_elf_file.h
+	$(Q) xxd -i upb/pb/jit_debug_elf_file.o > upb/pb/jit_debug_elf_file.h
+upb/pb/decoder_x86.h: upb/pb/jit_debug_elf_file.h
 endif
 
 # Function to expand a wildcard pattern recursively.
@@ -188,16 +186,16 @@ rwildcard=$(strip $(foreach d,$(wildcard $1*),$(call rwildcard,$d/,$2)$(filter $
 
 
 
-# Regenerating the auto-generated files in src/.
-src/descriptor.pb: src/descriptor.proto
+# Regenerating the auto-generated files in upb/.
+upb/descriptor.pb: upb/descriptor.proto
 	@# TODO: replace with upbc
-	protoc src/descriptor.proto -osrc/descriptor.pb
+	protoc upb/descriptor.proto -oupb/descriptor.pb
 
-descriptorgen: src/descriptor.pb src/upbc
+descriptorgen: upb/descriptor.pb tools/upbc
 	@# Regenerate descriptor_const.h
-	./src/upbc -o src/descriptor src/descriptor.pb
+	./tools/upbc -o upb/descriptor upb/descriptor.pb
 
-src/upbc: src/upbc.c $(LIBUPB)
+tools/upbc: tools/upbc.c $(LIBUPB)
 
 # Language extensions.
 python: $(LIBUPB_PIC)
@@ -275,7 +273,7 @@ tests/test_table: tests/test_table.cc
 	$(E) CXX $<
 	$(Q) $(CXX) $(CXXFLAGS) $(CPPFLAGS) -Wno-deprecated -o $@ $< $(LIBUPB)
 
-tests/tests: src/libupb.a
+tests/tests: upb/libupb.a
 
 
 # Benchmarks. ##################################################################
@@ -398,4 +396,4 @@ LUAEXT=lang_ext/lua/upb.so
 lua: $(LUAEXT)
 lang_ext/lua/upb.so: lang_ext/lua/upb.c $(LIBUPB_PIC)
 	@echo CC lang_ext/lua/upb.c
-	@$(CC) $(CFLAGS) $(CPPFLAGS) $(LUA_CPPFLAGS) -fpic -shared -o $@ $< src/libupb_pic.a $(LUA_LDFLAGS)
+	@$(CC) $(CFLAGS) $(CPPFLAGS) $(LUA_CPPFLAGS) -fpic -shared -o $@ $< upb/libupb_pic.a $(LUA_LDFLAGS)
diff --git a/benchmarks/parsestream.upb_table.c b/benchmarks/parsestream.upb_table.c
index a321010ed2..a4022b156b 100644
--- a/benchmarks/parsestream.upb_table.c
+++ b/benchmarks/parsestream.upb_table.c
@@ -2,10 +2,10 @@
 #include "main.c"
 
 #include <stdlib.h>
-#include "upb_def.h"
-#include "upb_decoder.h"
-#include "upb_strstream.h"
-#include "upb_glue.h"
+#include "upb/bytestream.h"
+#include "upb/def.h"
+#include "upb/pb/decoder.h"
+#include "upb/pb/glue.h"
 
 static char *input_str;
 static size_t input_len;
diff --git a/benchmarks/parsetostruct.upb_table.c b/benchmarks/parsetostruct.upb_table.c
index 76cbf2135b..88f355d3a1 100644
--- a/benchmarks/parsetostruct.upb_table.c
+++ b/benchmarks/parsetostruct.upb_table.c
@@ -1,11 +1,11 @@
 
 #include "main.c"
 
-#include "upb_def.h"
-#include "upb_decoder.h"
-#include "upb_strstream.h"
-#include "upb_glue.h"
-#include "upb_msg.h"
+#include "upb/bytestream.h"
+#include "upb/def.h"
+#include "upb/msg.h"
+#include "upb/pb/decoder.h"
+#include "upb/pb/glue.h"
 
 static upb_msgdef *def;
 static size_t len;
diff --git a/src/upb_stdio.h b/src/upb_stdio.h
deleted file mode 100644
index 858830cadb..0000000000
--- a/src/upb_stdio.h
+++ /dev/null
@@ -1,71 +0,0 @@
-/*
- * upb - a minimalist implementation of protocol buffers.
- *
- * Copyright (c) 2010 Google Inc.  See LICENSE for details.
- * Author: Josh Haberman <jhaberman@gmail.com>
- *
- * This file provides upb_bytesrc and upb_bytesink implementations for
- * ANSI C stdio, which is less efficient than posixfd, but more portable.
- *
- * Specifically, stdio functions acquire locks on every operation (unless you
- * use the f{read,write,...}_unlocked variants, which are not standard) and
- * performs redundant buffering (unless you disable it with setvbuf(), but we
- * can only do this on newly-opened filehandles).
- */
-
-#include <stdio.h>
-#include "upb_bytestream.h"
-
-#ifndef UPB_STDIO_H_
-#define UPB_STDIO_H_
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-typedef struct {
-  uint64_t ofs;
-  uint32_t refcount;
-  char data[];
-} upb_stdio_buf;
-
-// We use a single object for both bytesrc and bytesink for simplicity.
-// The object is still not thread-safe, and may only be used by one reader
-// and one writer at a time.
-typedef struct {
-  upb_bytesrc src;
-  upb_bytesink sink;
-  FILE *file;
-  bool should_close;
-  upb_stdio_buf **bufs;
-  uint32_t nbuf, szbuf;
-} upb_stdio;
-
-void upb_stdio_init(upb_stdio *stdio);
-// Caller should call upb_stdio_flush prior to calling this to ensure that
-// all data is flushed, otherwise data can be silently dropped if an error
-// occurs flushing the remaining buffers.
-void upb_stdio_uninit(upb_stdio *stdio);
-
-// Resets the object to read/write to the given "file."  The caller is
-// responsible for closing the file, which must outlive this object.
-void upb_stdio_reset(upb_stdio *stdio, FILE *file);
-
-// As an alternative to upb_stdio_reset(), initializes the object by opening a
-// file, and will handle closing it.  This may result in more efficient I/O
-// than the previous since we can call setvbuf() to disable buffering.
-void upb_stdio_open(upb_stdio *stdio, const char *filename, const char *mode,
-                    upb_status *s);
-
-// Must be called to cleanup after the object, including closing the file if
-// it was opened with upb_stdio_open() (which can fail, hence the status).
-//
-
-upb_bytesrc *upb_stdio_bytesrc(upb_stdio *stdio);
-upb_bytesink *upb_stdio_bytesink(upb_stdio *stdio);
-
-#ifdef __cplusplus
-}  /* extern "C" */
-#endif
-
-#endif
diff --git a/src/upb_strstream.c b/src/upb_strstream.c
deleted file mode 100644
index 9e17d75b1b..0000000000
--- a/src/upb_strstream.c
+++ /dev/null
@@ -1,106 +0,0 @@
-/*
- * upb - a minimalist implementation of protocol buffers.
- *
- * Copyright (c) 2010 Google Inc.  See LICENSE for details.
- * Author: Josh Haberman <jhaberman@gmail.com>
- */
-
-#include "upb_strstream.h"
-
-#include <stdlib.h>
-
-
-/* upb_stringsrc **************************************************************/
-
-size_t upb_stringsrc_fetch(void *_src, uint64_t ofs, upb_status *s) {
-  upb_stringsrc *src = _src;
-  size_t bytes = src->len - ofs;
-  if (bytes == 0) s->code = UPB_EOF;
-  return bytes;
-}
-
-void upb_stringsrc_read(void *_src, uint64_t src_ofs, size_t len, char *dst) {
-  upb_stringsrc *src = _src;
-  memcpy(dst, src->str + src_ofs, len);
-}
-
-const char *upb_stringsrc_getptr(void *_src, uint64_t ofs, size_t *len) {
-  upb_stringsrc *src = _src;
-  *len = src->len - ofs;
-  return src->str + ofs;
-}
-
-void upb_stringsrc_init(upb_stringsrc *s) {
-  static upb_bytesrc_vtbl vtbl = {
-    &upb_stringsrc_fetch,
-    &upb_stringsrc_read,
-    &upb_stringsrc_getptr,
-    NULL, NULL, NULL, NULL
-  };
-  upb_bytesrc_init(&s->bytesrc, &vtbl);
-  s->str = NULL;
-}
-
-void upb_stringsrc_reset(upb_stringsrc *s, const char *str, size_t len) {
-  s->str = str;
-  s->len = len;
-}
-
-void upb_stringsrc_uninit(upb_stringsrc *s) { (void)s; }
-
-upb_bytesrc *upb_stringsrc_bytesrc(upb_stringsrc *s) {
-  return &s->bytesrc;
-}
-
-
-/* upb_stringsink *************************************************************/
-
-void upb_stringsink_uninit(upb_stringsink *s) {
-  free(s->str);
-}
-
-// Resets the stringsink to a state where it will append to the given string.
-// The string must be newly created or recycled.  The stringsink will take a
-// reference on the string, so the caller need not ensure that it outlives the
-// stringsink.  A stringsink can be reset multiple times.
-void upb_stringsink_reset(upb_stringsink *s, char *str, size_t size) {
-  free(s->str);
-  s->str = str;
-  s->len = 0;
-  s->size = size;
-}
-
-upb_bytesink *upb_stringsink_bytesink(upb_stringsink *s) {
-  return &s->bytesink;
-}
-
-static int32_t upb_stringsink_vprintf(void *_s, upb_status *status,
-                                      const char *fmt, va_list args) {
-  (void)status;  // TODO: report realloc() errors.
-  upb_stringsink *s = _s;
-  int ret = upb_vrprintf(&s->str, &s->size, s->len, fmt, args);
-  if (ret >= 0) s->len += ret;
-  return ret;
-}
-
-bool upb_stringsink_write(void *_s, const char *buf, size_t len,
-                          upb_status *status) {
-  (void)status;  // TODO: report realloc() errors.
-  upb_stringsink *s = _s;
-  if (s->len + len > s->size) {
-    while(s->len + len > s->size) s->size *= 2;
-    s->str = realloc(s->str, s->size);
-  }
-  memcpy(s->str + s->len, buf, len);
-  s->len += len;
-  return true;
-}
-
-void upb_stringsink_init(upb_stringsink *s) {
-  static upb_bytesink_vtbl vtbl = {
-    upb_stringsink_write,
-    upb_stringsink_vprintf
-  };
-  upb_bytesink_init(&s->bytesink, &vtbl);
-  s->str = NULL;
-}
diff --git a/src/upb_strstream.h b/src/upb_strstream.h
deleted file mode 100644
index e57406eb89..0000000000
--- a/src/upb_strstream.h
+++ /dev/null
@@ -1,72 +0,0 @@
-/*
- * upb - a minimalist implementation of protocol buffers.
- *
- * Copyright (c) 2009-2010 Google Inc.  See LICENSE for details.
- * Author: Josh Haberman <jhaberman@gmail.com>
- *
- * This file contains upb_bytesrc and upb_bytesink implementations for
- * upb_string.
- */
-
-#ifndef UPB_STRSTREAM_H
-#define UPB_STRSTREAM_H
-
-#include "upb_bytestream.h"
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-/* upb_stringsrc **************************************************************/
-
-struct _upb_stringsrc {
-  upb_bytesrc bytesrc;
-  const char *str;
-  size_t len;
-};
-typedef struct _upb_stringsrc upb_stringsrc;
-
-// Create/free a stringsrc.
-void upb_stringsrc_init(upb_stringsrc *s);
-void upb_stringsrc_uninit(upb_stringsrc *s);
-
-// Resets the stringsrc to a state where it will vend the given string.  The
-// stringsrc will take a reference on the string, so the caller need not ensure
-// that it outlives the stringsrc.  A stringsrc can be reset multiple times.
-void upb_stringsrc_reset(upb_stringsrc *s, const char *str, size_t len);
-
-// Returns the upb_bytesrc* for this stringsrc.
-upb_bytesrc *upb_stringsrc_bytesrc(upb_stringsrc *s);
-
-
-/* upb_stringsink *************************************************************/
-
-struct _upb_stringsink {
-  upb_bytesink bytesink;
-  char *str;
-  size_t len, size;
-};
-typedef struct _upb_stringsink upb_stringsink;
-
-// Create/free a stringsrc.
-void upb_stringsink_init(upb_stringsink *s);
-void upb_stringsink_uninit(upb_stringsink *s);
-
-// Resets the sink's string to "str", which the sink takes ownership of.
-// "str" may be NULL, which will make the sink allocate a new string.
-void upb_stringsink_reset(upb_stringsink *s, char *str, size_t size);
-
-// Releases ownership of the returned string (which is "len" bytes long) and
-// resets the internal string to be empty again (as if reset were called with
-// NULL).
-const char *upb_stringsink_release(upb_stringsink *s, size_t *len);
-
-// Returns the upb_bytesink* for this stringsrc.  Invalidated by reset above.
-upb_bytesink *upb_stringsink_bytesink();
-
-
-#ifdef __cplusplus
-}  /* extern "C" */
-#endif
-
-#endif
diff --git a/tests/test_decoder.c b/tests/test_decoder.c
index 1c3bed01b5..88b87416f8 100644
--- a/tests/test_decoder.c
+++ b/tests/test_decoder.c
@@ -1,9 +1,9 @@
 
 #include <stdlib.h>
-#include "upb_decoder.h"
-#include "upb_textprinter.h"
-#include "upb_stdio.h"
-#include "upb_glue.h"
+#include "upb/bytestream.h"
+#include "upb/pb/decoder.h"
+#include "upb/pb/glue.h"
+#include "upb/pb/textprinter.h"
 
 int main(int argc, char *argv[]) {
   if (argc < 3) {
@@ -23,14 +23,12 @@ int main(int argc, char *argv[]) {
   upb_read_descriptor(symtab, desc, desc_len, &status);
   if (!upb_ok(&status)) {
     fprintf(stderr, "Error parsing descriptor: ");
-    upb_printerr(&status);
+    upb_status_print(&status, stderr);
     return 1;
   }
   free((void*)desc);
 
-  upb_string *name = upb_strdupc(argv[2]);
-  upb_def *md = upb_symtab_lookup(symtab, name);
-  upb_string_unref(name);
+  upb_def *md = upb_symtab_lookup(symtab, argv[2]);
   if (!md) {
     fprintf(stderr, "Descriptor did not contain message: %s\n", argv[2]);
     return 1;
@@ -57,12 +55,12 @@ int main(int argc, char *argv[]) {
   upb_decoder_initforhandlers(&d, handlers);
   upb_decoder_reset(&d, upb_stdio_bytesrc(&in), 0, UINT64_MAX, p);
 
-  upb_clearerr(&status);
+  upb_status_clear(&status);
   upb_decoder_decode(&d, &status);
 
   if (!upb_ok(&status)) {
     fprintf(stderr, "Error parsing input: ");
-    upb_printerr(&status);
+    upb_status_print(&status, stderr);
   }
 
   upb_status_uninit(&status);
diff --git a/tests/test_def.c b/tests/test_def.c
index 248d14a2f4..1f014f62fd 100644
--- a/tests/test_def.c
+++ b/tests/test_def.c
@@ -1,6 +1,6 @@
 
 #undef NDEBUG  /* ensure tests always assert. */
-#include "upb_def.h"
+#include "upb/def.h"
 #include <stdlib.h>
 
 int main() {
diff --git a/tests/test_table.cc b/tests/test_table.cc
index 0b47874ce6..8d98f2c40b 100644
--- a/tests/test_table.cc
+++ b/tests/test_table.cc
@@ -1,15 +1,16 @@
 
 #undef NDEBUG  /* ensure tests always assert. */
-#include "upb_table.h"
+#include "upb/table.h"
 #include "test_util.h"
 #include <assert.h>
+#include <string.h>
+#include <sys/resource.h>
+#include <ext/hash_map>
+#include <iostream>
 #include <map>
+#include <set>
 #include <string>
 #include <vector>
-#include <set>
-#include <ext/hash_map>
-#include <sys/resource.h>
-#include <iostream>
 
 bool benchmark = false;
 #define CPU_TIME_PER_TEST 0.5
diff --git a/tests/test_varint.c b/tests/test_varint.c
index 97902959ea..7dce6ab44c 100644
--- a/tests/test_varint.c
+++ b/tests/test_varint.c
@@ -4,7 +4,7 @@
  * Copyright (c) 2011 Google Inc.  See LICENSE for details.
  */
 
-#include "upb_varint.h"
+#include "upb/pb/varint.h"
 #include "upb_test.h"
 
 static void test_varint_decoder(upb_decoderet (*decoder)(const char*)) {
diff --git a/tests/test_vs_proto2.cc b/tests/test_vs_proto2.cc
index d220ff3d78..0444d40bfb 100644
--- a/tests/test_vs_proto2.cc
+++ b/tests/test_vs_proto2.cc
@@ -11,10 +11,10 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <google/protobuf/descriptor.h>
+#include "upb/def.h"
+#include "upb/msg.h"
+#include "upb/pb/glue.h"
 #include "upb_test.h"
-#include "upb_def.h"
-#include "upb_glue.h"
-#include "upb_msg.h"
 
 #include MESSAGE_HFILE
 
diff --git a/tests/tests.c b/tests/tests.c
index aa692f63bd..5cbbd785d7 100644
--- a/tests/tests.c
+++ b/tests/tests.c
@@ -2,11 +2,11 @@
 #include <assert.h>
 #include <stdio.h>
 #include <stdlib.h>
-#include "upb_def.h"
-#include "upb_glue.h"
+#include "upb/def.h"
+#include "upb/handlers.h"
+#include "upb/pb/decoder.h"
+#include "upb/pb/glue.h"
 #include "upb_test.h"
-#include "upb_handlers.h"
-#include "upb_decoder.h"
 
 static upb_symtab *load_test_proto() {
   upb_symtab *s = upb_symtab_new();
diff --git a/src/upbc.c b/tools/upbc.c
similarity index 100%
rename from src/upbc.c
rename to tools/upbc.c
diff --git a/src/upb_atomic.h b/upb/atomic.h
similarity index 100%
rename from src/upb_atomic.h
rename to upb/atomic.h
diff --git a/src/upb_stdio.c b/upb/bytestream.c
similarity index 60%
rename from src/upb_stdio.c
rename to upb/bytestream.c
index 20a3c15101..846b8ee6eb 100644
--- a/src/upb_stdio.c
+++ b/upb/bytestream.c
@@ -5,7 +5,7 @@
  * Author: Josh Haberman <jhaberman@gmail.com>
  */
 
-#include "upb_stdio.h"
+#include "upb/bytestream.h"
 
 #include <stddef.h>
 #include <stdlib.h>
@@ -14,8 +14,14 @@
 // We can make this configurable if necessary.
 #define BUF_SIZE 32768
 
+char *upb_strref_dup(struct _upb_strref *r) {
+  char *ret = (char*)malloc(r->len + 1);
+  upb_bytesrc_read(r->bytesrc, r->stream_offset, r->len, ret);
+  ret[r->len] = '\0';
+  return ret;
+}
 
-/* upb_bytesrc methods ********************************************************/
+/* upb_stdio ******************************************************************/
 
 int upb_stdio_cmpbuf(const void *_key, const void *_elem) {
   const uint64_t *ofs = _key;
@@ -93,9 +99,6 @@ void upb_stdio_unrefregion(void *src, uint64_t ofs, size_t len) {
   (void)len;
 }
 
-
-/* upb_bytesink methods *******************************************************/
-
 #if 0
 upb_strlen_t upb_stdio_putstr(upb_bytesink *sink, upb_string *str, upb_status *status) {
   upb_stdio *stdio = (upb_stdio*)((char*)sink - offsetof(upb_stdio, sink));
@@ -164,3 +167,99 @@ void upb_stdio_uninit(upb_stdio *stdio) {
 
 upb_bytesrc* upb_stdio_bytesrc(upb_stdio *stdio) { return &stdio->src; }
 upb_bytesink* upb_stdio_bytesink(upb_stdio *stdio) { return &stdio->sink; }
+
+
+/* upb_stringsrc **************************************************************/
+
+size_t upb_stringsrc_fetch(void *_src, uint64_t ofs, upb_status *s) {
+  upb_stringsrc *src = _src;
+  size_t bytes = src->len - ofs;
+  if (bytes == 0) s->code = UPB_EOF;
+  return bytes;
+}
+
+void upb_stringsrc_read(void *_src, uint64_t src_ofs, size_t len, char *dst) {
+  upb_stringsrc *src = _src;
+  memcpy(dst, src->str + src_ofs, len);
+}
+
+const char *upb_stringsrc_getptr(void *_src, uint64_t ofs, size_t *len) {
+  upb_stringsrc *src = _src;
+  *len = src->len - ofs;
+  return src->str + ofs;
+}
+
+void upb_stringsrc_init(upb_stringsrc *s) {
+  static upb_bytesrc_vtbl vtbl = {
+    &upb_stringsrc_fetch,
+    &upb_stringsrc_read,
+    &upb_stringsrc_getptr,
+    NULL, NULL, NULL, NULL
+  };
+  upb_bytesrc_init(&s->bytesrc, &vtbl);
+  s->str = NULL;
+}
+
+void upb_stringsrc_reset(upb_stringsrc *s, const char *str, size_t len) {
+  s->str = str;
+  s->len = len;
+}
+
+void upb_stringsrc_uninit(upb_stringsrc *s) { (void)s; }
+
+upb_bytesrc *upb_stringsrc_bytesrc(upb_stringsrc *s) {
+  return &s->bytesrc;
+}
+
+
+/* upb_stringsink *************************************************************/
+
+void upb_stringsink_uninit(upb_stringsink *s) {
+  free(s->str);
+}
+
+// Resets the stringsink to a state where it will append to the given string.
+// The string must be newly created or recycled.  The stringsink will take a
+// reference on the string, so the caller need not ensure that it outlives the
+// stringsink.  A stringsink can be reset multiple times.
+void upb_stringsink_reset(upb_stringsink *s, char *str, size_t size) {
+  free(s->str);
+  s->str = str;
+  s->len = 0;
+  s->size = size;
+}
+
+upb_bytesink *upb_stringsink_bytesink(upb_stringsink *s) {
+  return &s->bytesink;
+}
+
+static int32_t upb_stringsink_vprintf(void *_s, upb_status *status,
+                                      const char *fmt, va_list args) {
+  (void)status;  // TODO: report realloc() errors.
+  upb_stringsink *s = _s;
+  int ret = upb_vrprintf(&s->str, &s->size, s->len, fmt, args);
+  if (ret >= 0) s->len += ret;
+  return ret;
+}
+
+bool upb_stringsink_write(void *_s, const char *buf, size_t len,
+                          upb_status *status) {
+  (void)status;  // TODO: report realloc() errors.
+  upb_stringsink *s = _s;
+  if (s->len + len > s->size) {
+    while(s->len + len > s->size) s->size *= 2;
+    s->str = realloc(s->str, s->size);
+  }
+  memcpy(s->str + s->len, buf, len);
+  s->len += len;
+  return true;
+}
+
+void upb_stringsink_init(upb_stringsink *s) {
+  static upb_bytesink_vtbl vtbl = {
+    upb_stringsink_write,
+    upb_stringsink_vprintf
+  };
+  upb_bytesink_init(&s->bytesink, &vtbl);
+  s->str = NULL;
+}
diff --git a/src/upb_bytestream.h b/upb/bytestream.h
similarity index 61%
rename from src/upb_bytestream.h
rename to upb/bytestream.h
index 836abb0868..2a6f7d20a9 100644
--- a/src/upb_bytestream.h
+++ b/upb/bytestream.h
@@ -52,9 +52,9 @@ INLINE void upb_bytesrc_init(upb_bytesrc *src, upb_bytesrc_vtbl *vtbl) {
   src->vtbl = vtbl;
 }
 
-// Fetches at least minlen bytes starting at ofs, returning the actual number
-// of bytes fetched (or 0 on error: see "s" for details).  Gives caller a ref
-// on the fetched region.  It is safe to re-fetch existing regions but only if
+// Fetches at least one byte starting at ofs, returning the actual number of
+// bytes fetched (or 0 on error: see "s" for details).  Gives caller a ref on
+// the fetched region.  It is safe to re-fetch existing regions but only if
 // they are ref'd.  "ofs" may not greater than the end of the region that was
 // previously fetched.
 INLINE size_t upb_bytesrc_fetch(upb_bytesrc *src, uint64_t ofs, upb_status *s) {
@@ -135,12 +135,7 @@ typedef struct _upb_strref {
 
 // Copies the contents of the strref into a newly-allocated, NULL-terminated
 // string.
-INLINE char *upb_strref_dup(struct _upb_strref *r) {
-  char *ret = (char*)malloc(r->len + 1);
-  upb_bytesrc_read(r->bytesrc, r->stream_offset, r->len, ret);
-  ret[r->len] = '\0';
-  return ret;
-}
+char *upb_strref_dup(struct _upb_strref *r);
 
 
 /* upb_bytesink ***************************************************************/
@@ -187,9 +182,102 @@ INLINE int32_t upb_bytesink_printf(upb_bytesink *sink, upb_status *status,
 // TODO: add flush()
 
 
-/* upb_cbuf *******************************************************************/
+/* upb_stdio ******************************************************************/
+
+// bytesrc/bytesink for ANSI C stdio, which is less efficient than posixfd, but
+// more portable.
+//
+// Specifically, stdio functions acquire locks on every operation (unless you
+// use the f{read,write,...}_unlocked variants, which are not standard) and
+// performs redundant buffering (unless you disable it with setvbuf(), but we
+// can only do this on newly-opened filehandles).
 
-// A circular buffer implementation for bytesrcs that do internal buffering.
+typedef struct {
+  uint64_t ofs;
+  uint32_t refcount;
+  char data[];
+} upb_stdio_buf;
+
+// We use a single object for both bytesrc and bytesink for simplicity.
+// The object is still not thread-safe, and may only be used by one reader
+// and one writer at a time.
+typedef struct {
+  upb_bytesrc src;
+  upb_bytesink sink;
+  FILE *file;
+  bool should_close;
+  upb_stdio_buf **bufs;
+  uint32_t nbuf, szbuf;
+} upb_stdio;
+
+void upb_stdio_init(upb_stdio *stdio);
+// Caller should call upb_stdio_flush prior to calling this to ensure that
+// all data is flushed, otherwise data can be silently dropped if an error
+// occurs flushing the remaining buffers.
+void upb_stdio_uninit(upb_stdio *stdio);
+
+// Resets the object to read/write to the given "file."  The caller is
+// responsible for closing the file, which must outlive this object.
+void upb_stdio_reset(upb_stdio *stdio, FILE *file);
+
+// As an alternative to upb_stdio_reset(), initializes the object by opening a
+// file, and will handle closing it.  This may result in more efficient I/O
+// than the previous since we can call setvbuf() to disable buffering.
+void upb_stdio_open(upb_stdio *stdio, const char *filename, const char *mode,
+                    upb_status *s);
+
+upb_bytesrc *upb_stdio_bytesrc(upb_stdio *stdio);
+upb_bytesink *upb_stdio_bytesink(upb_stdio *stdio);
+
+
+/* upb_stringsrc **************************************************************/
+
+// bytesrc/bytesink for a simple contiguous string.
+
+struct _upb_stringsrc {
+  upb_bytesrc bytesrc;
+  const char *str;
+  size_t len;
+};
+typedef struct _upb_stringsrc upb_stringsrc;
+
+// Create/free a stringsrc.
+void upb_stringsrc_init(upb_stringsrc *s);
+void upb_stringsrc_uninit(upb_stringsrc *s);
+
+// Resets the stringsrc to a state where it will vend the given string.  The
+// stringsrc will take a reference on the string, so the caller need not ensure
+// that it outlives the stringsrc.  A stringsrc can be reset multiple times.
+void upb_stringsrc_reset(upb_stringsrc *s, const char *str, size_t len);
+
+// Returns the upb_bytesrc* for this stringsrc.
+upb_bytesrc *upb_stringsrc_bytesrc(upb_stringsrc *s);
+
+
+/* upb_stringsink *************************************************************/
+
+struct _upb_stringsink {
+  upb_bytesink bytesink;
+  char *str;
+  size_t len, size;
+};
+typedef struct _upb_stringsink upb_stringsink;
+
+// Create/free a stringsrc.
+void upb_stringsink_init(upb_stringsink *s);
+void upb_stringsink_uninit(upb_stringsink *s);
+
+// Resets the sink's string to "str", which the sink takes ownership of.
+// "str" may be NULL, which will make the sink allocate a new string.
+void upb_stringsink_reset(upb_stringsink *s, char *str, size_t size);
+
+// Releases ownership of the returned string (which is "len" bytes long) and
+// resets the internal string to be empty again (as if reset were called with
+// NULL).
+const char *upb_stringsink_release(upb_stringsink *s, size_t *len);
+
+// Returns the upb_bytesink* for this stringsrc.  Invalidated by reset above.
+upb_bytesink *upb_stringsink_bytesink();
 
 #ifdef __cplusplus
 }  /* extern "C" */
diff --git a/src/upb_def.c b/upb/def.c
similarity index 99%
rename from src/upb_def.c
rename to upb/def.c
index 4cd80b1269..000b7f2557 100644
--- a/src/upb_def.c
+++ b/upb/def.c
@@ -8,7 +8,7 @@
 #include <stdlib.h>
 #include <stddef.h>
 #include <string.h>
-#include "upb_def.h"
+#include "upb/def.h"
 
 #define alignof(t) offsetof(struct { char c; t x; }, x)
 
diff --git a/src/upb_def.h b/upb/def.h
similarity index 99%
rename from src/upb_def.h
rename to upb/def.h
index 34f5009334..4a7a01712c 100644
--- a/src/upb_def.h
+++ b/upb/def.h
@@ -19,8 +19,8 @@
 #ifndef UPB_DEF_H_
 #define UPB_DEF_H_
 
-#include "upb_atomic.h"
-#include "upb_table.h"
+#include "upb/atomic.h"
+#include "upb/table.h"
 
 #ifdef __cplusplus
 extern "C" {
diff --git a/src/upb_descriptor.c b/upb/descriptor.c
similarity index 99%
rename from src/upb_descriptor.c
rename to upb/descriptor.c
index f70f1bab9a..48f0165ada 100644
--- a/src/upb_descriptor.c
+++ b/upb/descriptor.c
@@ -5,11 +5,10 @@
  * Author: Josh Haberman <jhaberman@gmail.com>
  */
 
-#include "upb_descriptor.h"
-
 #include <stdlib.h>
 #include <errno.h>
-#include "upb_def.h"
+#include "upb/def.h"
+#include "upb/descriptor.h"
 
 // Returns a newly allocated string that joins input strings together, for example:
 //   join("Foo.Bar", "Baz") -> "Foo.Bar.Baz"
diff --git a/src/upb_descriptor.h b/upb/descriptor.h
similarity index 98%
rename from src/upb_descriptor.h
rename to upb/descriptor.h
index ee05e2f9f9..4d658fb4fa 100644
--- a/src/upb_descriptor.h
+++ b/upb/descriptor.h
@@ -12,7 +12,7 @@
 #ifndef UPB_DESCRIPTOR_H
 #define UPB_DESCRIPTOR_H
 
-#include "upb_handlers.h"
+#include "upb/handlers.h"
 
 #ifdef __cplusplus
 extern "C" {
diff --git a/src/descriptor.proto b/upb/descriptor.proto
similarity index 100%
rename from src/descriptor.proto
rename to upb/descriptor.proto
diff --git a/src/descriptor_const.h b/upb/descriptor_const.h
similarity index 100%
rename from src/descriptor_const.h
rename to upb/descriptor_const.h
diff --git a/src/upb_handlers.c b/upb/handlers.c
similarity index 99%
rename from src/upb_handlers.c
rename to upb/handlers.c
index f513dfd38b..05300c0cc1 100644
--- a/src/upb_handlers.c
+++ b/upb/handlers.c
@@ -6,7 +6,7 @@
  */
 
 #include <stdlib.h>
-#include "upb_handlers.h"
+#include "upb/handlers.h"
 
 
 /* upb_mhandlers **************************************************************/
diff --git a/src/upb_handlers.h b/upb/handlers.h
similarity index 99%
rename from src/upb_handlers.h
rename to upb/handlers.h
index 1ccc59f02a..e3d91cfc30 100644
--- a/src/upb_handlers.h
+++ b/upb/handlers.h
@@ -15,9 +15,9 @@
 #define UPB_HANDLERS_H
 
 #include <limits.h>
-#include "upb.h"
-#include "upb_def.h"
-#include "upb_bytestream.h"
+#include "upb/upb.h"
+#include "upb/def.h"
+#include "upb/bytestream.h"
 
 #ifdef __cplusplus
 extern "C" {
diff --git a/src/upb_msg.c b/upb/msg.c
similarity index 99%
rename from src/upb_msg.c
rename to upb/msg.c
index 83fa6ff49b..a2b2cf72fe 100644
--- a/src/upb_msg.c
+++ b/upb/msg.c
@@ -7,8 +7,8 @@
  * Data structure for storing a message of protobuf data.
  */
 
-#include "upb.h"
-#include "upb_msg.h"
+#include "upb/upb.h"
+#include "upb/msg.h"
 
 void upb_msg_clear(void *msg, upb_msgdef *md) {
   memset(msg, 0, md->hasbit_bytes);
diff --git a/src/upb_msg.h b/upb/msg.h
similarity index 99%
rename from src/upb_msg.h
rename to upb/msg.h
index af328e3ab8..625d805d60 100644
--- a/src/upb_msg.h
+++ b/upb/msg.h
@@ -26,8 +26,8 @@
 #define UPB_MSG_H
 
 #include <stdlib.h>
-#include "upb_def.h"
-#include "upb_handlers.h"
+#include "upb/def.h"
+#include "upb/handlers.h"
 
 #ifdef __cplusplus
 extern "C" {
diff --git a/src/upb_decoder.c b/upb/pb/decoder.c
similarity index 98%
rename from src/upb_decoder.c
rename to upb/pb/decoder.c
index fed48af604..218c7803bb 100644
--- a/src/upb_decoder.c
+++ b/upb/pb/decoder.c
@@ -8,11 +8,10 @@
 #include <inttypes.h>
 #include <stddef.h>
 #include <stdlib.h>
-#include "bswap.h"
-#include "upb_bytestream.h"
-#include "upb_decoder.h"
-#include "upb_varint.h"
-#include "upb_msg.h"
+#include "upb/bytestream.h"
+#include "upb/msg.h"
+#include "upb/pb/decoder.h"
+#include "upb/pb/varint.h"
 
 // Used for frames that have no specific end offset: groups, repeated primitive
 // fields inside groups, and the top-level message.
@@ -23,7 +22,7 @@
 #define Dst_REF (d->dynasm)
 #define Dst (d)
 #include "dynasm/dasm_proto.h"
-#include "upb_decoder_x86.h"
+#include "upb/pb/decoder_x86.h"
 #endif
 
 // It's unfortunate that we have to micro-manage the compiler this way,
@@ -201,12 +200,12 @@ FORCEINLINE void upb_decode_fixed(upb_decoder *d, char *buf, size_t bytes) {
 FORCEINLINE uint32_t upb_decode_fixed32(upb_decoder *d) {
   uint32_t u32;
   upb_decode_fixed(d, (char*)&u32, sizeof(uint32_t));
-  return le32toh(u32);
+  return u32;  // TODO: proper byte swapping
 }
 FORCEINLINE uint64_t upb_decode_fixed64(upb_decoder *d) {
   uint64_t u64;
   upb_decode_fixed(d, (char*)&u64, sizeof(uint64_t));
-  return le64toh(u64);
+  return u64;  // TODO: proper byte swapping
 }
 
 INLINE upb_strref *upb_decode_string(upb_decoder *d) {
diff --git a/src/upb_decoder.h b/upb/pb/decoder.h
similarity index 99%
rename from src/upb_decoder.h
rename to upb/pb/decoder.h
index 7a813bfb77..398135903b 100644
--- a/src/upb_decoder.h
+++ b/upb/pb/decoder.h
@@ -20,7 +20,7 @@
 #include <setjmp.h>
 #include <stdbool.h>
 #include <stdint.h>
-#include "upb_handlers.h"
+#include "upb/handlers.h"
 
 #ifdef __cplusplus
 extern "C" {
diff --git a/src/upb_decoder_x86.dasc b/upb/pb/decoder_x86.dasc
similarity index 99%
rename from src/upb_decoder_x86.dasc
rename to upb/pb/decoder_x86.dasc
index 800b099a1b..19043c6b5f 100644
--- a/src/upb_decoder_x86.dasc
+++ b/upb/pb/decoder_x86.dasc
@@ -40,7 +40,7 @@
 // for a few magic numbers and doing a dumb string replacement.
 
 #ifndef __APPLE__
-#include "jit_debug_elf_file.h"
+#include "upb/pb/jit_debug_elf_file.h"
 
 typedef enum
 {
@@ -69,9 +69,9 @@ void __attribute__((noinline)) __jit_debug_register_code() { __asm__ __volatile_
 
 void upb_reg_jit_gdb(upb_decoder *d) {
   // Create debug info.
-  size_t elf_len = src_jit_debug_elf_file_o_len;
+  size_t elf_len = upb_pb_jit_debug_elf_file_o_len;
   d->debug_info = malloc(elf_len);
-  memcpy(d->debug_info, src_jit_debug_elf_file_o, elf_len);
+  memcpy(d->debug_info, upb_pb_jit_debug_elf_file_o, elf_len);
   uint64_t *p = (void*)d->debug_info;
   for (; (void*)(p+1) <= (void*)d->debug_info + elf_len; ++p) {
     if (*p == 0x12345678) { *p = (uintptr_t)d->jit_code; }
@@ -270,7 +270,7 @@ void upb_reg_jit_gdb(upb_decoder *d) {
 |.endmacro
 
 #include <stdlib.h>
-#include "upb_varint.h"
+#include "upb/pb/varint.h"
 
 // PTR should point to the beginning of the tag.
 static void upb_decoder_jit_field(upb_decoder *d, uint32_t tag, uint32_t next_tag,
diff --git a/src/upb_encoder.c b/upb/pb/encoder.c
similarity index 100%
rename from src/upb_encoder.c
rename to upb/pb/encoder.c
diff --git a/src/upb_encoder.h b/upb/pb/encoder.h
similarity index 100%
rename from src/upb_encoder.h
rename to upb/pb/encoder.h
diff --git a/src/upb_glue.c b/upb/pb/glue.c
similarity index 95%
rename from src/upb_glue.c
rename to upb/pb/glue.c
index 1f5bd3fedb..3763ae09c0 100644
--- a/src/upb_glue.c
+++ b/upb/pb/glue.c
@@ -5,12 +5,12 @@
  * Author: Josh Haberman <jhaberman@gmail.com>
  */
 
-#include "upb_decoder.h"
-#include "upb_descriptor.h"
-#include "upb_glue.h"
-#include "upb_msg.h"
-#include "upb_strstream.h"
-#include "upb_textprinter.h"
+#include "upb/bytestream.h"
+#include "upb/descriptor.h"
+#include "upb/msg.h"
+#include "upb/pb/decoder.h"
+#include "upb/pb/glue.h"
+#include "upb/pb/textprinter.h"
 
 void upb_strtomsg(const char *str, size_t len, void *msg, upb_msgdef *md,
                   upb_status *status) {
diff --git a/src/upb_glue.h b/upb/pb/glue.h
similarity index 99%
rename from src/upb_glue.h
rename to upb/pb/glue.h
index 0448c2f168..5359120ede 100644
--- a/src/upb_glue.h
+++ b/upb/pb/glue.h
@@ -27,7 +27,7 @@
 #define UPB_GLUE_H
 
 #include <stdbool.h>
-#include "upb.h"
+#include "upb/upb.h"
 
 #ifdef __cplusplus
 extern "C" {
diff --git a/src/jit_debug_elf_file.s b/upb/pb/jit_debug_elf_file.s
similarity index 100%
rename from src/jit_debug_elf_file.s
rename to upb/pb/jit_debug_elf_file.s
diff --git a/src/upb_textprinter.c b/upb/pb/textprinter.c
similarity index 98%
rename from src/upb_textprinter.c
rename to upb/pb/textprinter.c
index 14cce9b637..ce029d58ba 100644
--- a/src/upb_textprinter.c
+++ b/upb/pb/textprinter.c
@@ -5,12 +5,11 @@
  * Author: Josh Haberman <jhaberman@gmail.com>
  */
 
-#include "upb_textprinter.h"
-
 #include <ctype.h>
 #include <float.h>
 #include <inttypes.h>
 #include <stdlib.h>
+#include "upb/pb/textprinter.h"
 
 struct _upb_textprinter {
   upb_bytesink *bytesink;
@@ -29,7 +28,7 @@ static int upb_textprinter_putescaped(upb_textprinter *p, upb_strref *strref,
   char dstbuf[4096], *dst = dstbuf, *dstend = dstbuf + sizeof(dstbuf);
   char buf[strref->len], *src = buf;
   char *end = src + strref->len;
-  upb_strref_read(strref, src);
+  upb_bytesrc_read(strref->bytesrc, strref->stream_offset, strref->len, buf);
 
   // I think hex is prettier and more useful, but proto2 uses octal; should
   // investigate whether it can parse hex also.
diff --git a/src/upb_textprinter.h b/upb/pb/textprinter.h
similarity index 92%
rename from src/upb_textprinter.h
rename to upb/pb/textprinter.h
index 2d70d2e124..94552081bd 100644
--- a/src/upb_textprinter.h
+++ b/upb/pb/textprinter.h
@@ -8,8 +8,8 @@
 #ifndef UPB_TEXT_H_
 #define UPB_TEXT_H_
 
-#include "upb_bytestream.h"
-#include "upb_handlers.h"
+#include "upb/bytestream.h"
+#include "upb/handlers.h"
 
 #ifdef __cplusplus
 extern "C" {
diff --git a/src/upb_varint.c b/upb/pb/varint.c
similarity index 98%
rename from src/upb_varint.c
rename to upb/pb/varint.c
index 25052aaf23..45caec1a9f 100644
--- a/src/upb_varint.c
+++ b/upb/pb/varint.c
@@ -5,7 +5,7 @@
  * Author: Josh Haberman <jhaberman@gmail.com>
  */
 
-#include "upb_varint.h"
+#include "upb/pb/varint.h"
 
 // Given an encoded varint v, returns an integer with a single bit set that
 // indicates the end of the varint.  Subtracting one from this value will
diff --git a/src/upb_varint.h b/upb/pb/varint.h
similarity index 99%
rename from src/upb_varint.h
rename to upb/pb/varint.h
index 87fca2b732..1bbd193b0a 100644
--- a/src/upb_varint.h
+++ b/upb/pb/varint.h
@@ -11,9 +11,9 @@
 #ifndef UPB_VARINT_DECODER_H_
 #define UPB_VARINT_DECODER_H_
 
-#include "upb.h"
 #include <stdint.h>
 #include <string.h>
+#include "upb/upb.h"
 
 #ifdef __cplusplus
 extern "C" {
diff --git a/src/upb_table.c b/upb/table.c
similarity index 99%
rename from src/upb_table.c
rename to upb/table.c
index fc9e9deb90..71aca16bbf 100644
--- a/src/upb_table.c
+++ b/upb/table.c
@@ -8,7 +8,7 @@
  * can be useful for debugging.
  */
 
-#include "upb_table.h"
+#include "upb/table.h"
 
 #include <assert.h>
 #include <stdlib.h>
diff --git a/src/upb_table.h b/upb/table.h
similarity index 100%
rename from src/upb_table.h
rename to upb/table.h
diff --git a/src/upb.c b/upb/upb.c
similarity index 98%
rename from src/upb.c
rename to upb/upb.c
index 0f3ea18f0a..0ff082f38c 100644
--- a/src/upb.c
+++ b/upb/upb.c
@@ -10,9 +10,9 @@
 #include <stddef.h>
 #include <stdlib.h>
 #include <string.h>
-#include "descriptor_const.h"
-#include "upb.h"
-#include "upb_bytestream.h"
+#include "upb/descriptor_const.h"
+#include "upb/upb.h"
+#include "upb/bytestream.h"
 
 #define alignof(t) offsetof(struct { char c; t x; }, x)
 #define TYPE_INFO(wire_type, ctype, inmemory_type) \
diff --git a/src/upb.h b/upb/upb.h
similarity index 99%
rename from src/upb.h
rename to upb/upb.h
index b15340e4ab..153057df68 100644
--- a/src/upb.h
+++ b/upb/upb.h
@@ -15,7 +15,7 @@
 #include <stdio.h>  // only for size_t.
 #include <assert.h>
 #include "descriptor_const.h"
-#include "upb_atomic.h"
+#include "atomic.h"
 
 #ifdef __cplusplus
 extern "C" {