address comments

templates/src/objective-c/BoringSSL-GRPC.podspec.template

@@ -7,14 +7,27 @@
     import subprocess
     boringssl_commit = subprocess.check_output(['git', 'rev-parse', 'HEAD'], cwd='third_party/boringssl-with-bazel').decode().strip()
 
-    import gzip, shutil, os, base64
+    # Compress src/boringssl/boringssl_prefix_symbols.h with gzip then encode
+    # with Base64. The result is put in variable prefix_gz_b64.
+    #
+    # Note that gRPC's template parser is still using Python 2, whose gzip
+    # module does not support directly compressing bytes into bytes. Instead,
+    # we have to write the compressed bytes into a intermediate file
+    # (src/boringssl/boringssl_prefix_symbols.h.gz), read the compressed
+    # bytes from this file, then delete the intermediate file.
+    #
     # TODO(mxyan): move to python3 style gzip compression when possible
-    with open('src/boringssl/boringssl_prefix_symbols.h', 'rb') as f_in, gzip.GzipFile('src/boringssl/boringssl_prefix_symbols.h.gz', 'w', mtime=0.0) as f_out:
-      shutil.copyfileobj(f_in, f_out)
-    with open('src/boringssl/boringssl_prefix_symbols.h.gz', 'rb') as f_in:
-      prefix_gz = f_in.read()
-    os.remove('src/boringssl/boringssl_prefix_symbols.h.gz')
-    prefix_gz_b64 = base64.b64encode(prefix_gz)
+    def compress_boringssl_prefix_header():
+      import gzip, shutil, os, base64
+      with open('src/boringssl/boringssl_prefix_symbols.h', 'rb') as f_in, gzip.GzipFile('src/boringssl/boringssl_prefix_symbols.h.gz', 'w', mtime=0.0) as f_out:
+        shutil.copyfileobj(f_in, f_out)
+      with open('src/boringssl/boringssl_prefix_symbols.h.gz', 'rb') as f_in:
+        prefix_gz = f_in.read()
+      os.remove('src/boringssl/boringssl_prefix_symbols.h.gz')
+      prefix_gz_b64 = base64.b64encode(prefix_gz)
+      WRAP_LENGTH=80
+      prefix_gz_b64_wrapped = [prefix_gz_b64[i:i+WRAP_LENGTH] for i in range(0, len(prefix_gz_b64), WRAP_LENGTH)]
+      return prefix_gz_b64_wrapped
   %>
 
   # This file has been automatically generated from a template file.
@@ -230,12 +243,13 @@
       # /src/boringssl/boringssl_prefix_symbols.h. Here we decode the content and inject the header to
       # the correct location in BoringSSL.
       base64 -D <<EOF | gunzip > src/include/openssl/boringssl_prefix_symbols.h
-        ${prefix_gz_b64}
+        % for line in compress_boringssl_prefix_header():
+        ${line}
+        % endfor
       EOF
 
       # We are renaming openssl to openssl_grpc so that there is no conflict with openssl if it exists
       find . -type f \\( -path '*.h' -or -path '*.cc' -or -path '*.c' \\) -print0 | xargs -0 -L1 sed -E -i'.grpc_back' 's;#include <openssl/;#include <openssl_grpc/;g'
-      # BoringSSL include boringssl_prefix_symbols.h without any prefix, which does not match the
 
       # Include of boringssl_prefix_symbols.h does not follow Xcode import style. We add the package
       # name here so that Xcode knows where to find it.

tools/distrib/generate_boringssl_prefix_header.sh

@@ -31,23 +31,21 @@ cd ../../$BORINGSSL_ROOT
 BORINGSSL_COMMIT=$(git rev-parse HEAD)
 BORINGSSL_PREFIX_HEADERS_DIR=src/boringssl
 
-# generate the prefix header
 rm -rf build
 mkdir -p build
 cd build
 cmake ..
 make -j
-
 [ -f ssl/libssl.a ] || { echo "Failed to build libssl.a" ; exit 1 ; }
 [ -f crypto/libcrypto.a ] || { echo "Failed to build libcrypto.a" ; exit 1 ; }
 
+# Generates boringssl_prefix_symbols.h. The prefix header is generated by
+# BoringSSL's build system as instructed by BoringSSL build guide (see
+# https://github.com/google/boringssl/blob/367d64f84c3c1d01381c18c5a239b85eef47633c/BUILDING.md#building-with-prefixed-symbols).
 go run ../util/read_symbols.go ssl/libssl.a > ./symbols.txt
 go run ../util/read_symbols.go crypto/libcrypto.a >> ./symbols.txt
-
-# generates boringssl_prefix_symbols.h
 cmake .. -DBORINGSSL_PREFIX=GRPC -DBORINGSSL_PREFIX_SYMBOLS=symbols.txt
 make boringssl_prefix_symbols
-
 [ -f symbol_prefix_include/boringssl_prefix_symbols.h ] || { echo "Failed to build boringssl_prefix_symbols.sh" ; exit 1 ; }
 
 cd ../../../..