From a230cf5053ce553d92ba5efb51324149fae201b6 Mon Sep 17 00:00:00 2001 From: Joshua Haberman Date: Tue, 22 Dec 2009 06:11:58 -0800 Subject: [PATCH] More work. --- src/upb_data.c | 11 ++-- src/upb_data.h | 145 +++++++++++++++++++++++++++++++++++-------------- 2 files changed, 108 insertions(+), 48 deletions(-) diff --git a/src/upb_data.c b/src/upb_data.c index 66e9885416..3c8b244467 100644 --- a/src/upb_data.c +++ b/src/upb_data.c @@ -19,6 +19,10 @@ static uint32_t round_up_to_pow2(uint32_t v) return v; } +static void check_not_frozen(upb_data *d) { + if(upb_data_hasflag(d, UPB_DATA_FROZEN)) abort(); +} + upb_string *upb_string_new() { upb_string *s = malloc(sizeof(*s)); s->byte_size = 0; @@ -35,14 +39,9 @@ static void _upb_string_free(upb_string *s) free(s); } -INLINE upb_string *upb_string_getref(upb_string *s, upb_flags_t ref_flags) { - if((ref_flags == UPB_REF_FROZEN && !s->is_frozen && s - upb_atomic_read((void*)(s + 1)) > 1) || - (ref_flags == UPB_REF_MUTABLE && s->is_frozen && -} - char *upb_string_getrwbuf(upb_string *s, upb_strlen_t byte_len) { + check_not_frozen(s); if(s->byte_size < byte_len) { // Need to resize. s->byte_size = round_up_to_pow2(byte_len); diff --git a/src/upb_data.h b/src/upb_data.h index a15cb357fc..01661ffbf5 100644 --- a/src/upb_data.h +++ b/src/upb_data.h @@ -14,23 +14,58 @@ #include "upb.h" #include "upb_def.h" -// Set if the object itself was allocated with malloc() and should be freed -// with free(). This flag would be false if the object was allocated on the -// stack or is data from the static segment of an object file. Note that this -// flag does not apply to the data being referenced by a string or array. -// -// If this flag is false, UPB_FLAG_HAS_REFCOUNT must be false also; there is -// no sense refcounting something that does not need to be freed. -#define UPB_FLAG_IS_HEAP_ALLOCATED (1<<2) - -// Set if the object is frozen against modification. While an object is -// frozen, it is suitable for concurrent access. Note that this flag alone is -// not a sufficient mechanism for preventing any kind of writes to the object's -// memory, because the object could still have a refcount and/or reflist. -#define UPB_FLAG_IS_FROZEN (1<<3) - -// Set if the object has an embedded refcount. -#define UPB_FLAG_HAS_REFCOUNT (1<<4) +/* upb_data *******************************************************************/ + +// The "base class" of strings, arrays, and messages. Contains a few flags and +// possibly a reference count. None of the functions for upb_data are public, +// but some of the constants are. +typedef upb_atomic_t upb_data; + +// The flags in upb_data. +enum upb_data_flag { + // Set if the object itself was allocated with malloc() and should be freed + // with free(). This flag would be false if the object was allocated on the + // stack or is data from the static segment of an object file. Note that this + // flag does not apply to the data being referenced by a string or array. + // + // If this flag is false, UPB_FLAG_HAS_REFCOUNT must be false also; there is + // no sense refcounting something that does not need to be freed. + UPB_DATA_HEAPALLOCATED = 1, + + // Set if the object is frozen against modification. While an object is + // frozen, it is suitable for concurrent readonly access. Note that this + // flag alone is not a sufficient mechanism for preventing any kind of writes + // to the object's memory, because the object could still have a refcount. + UPB_DATA_FROZEN = (1<<1), + + // Set if the object has an embedded refcount. + UPB_DATA_REFCOUNTED = (1<<2) +}; + +#define REFCOUNT_MASK 0xFFFFFFF8 +#define REFCOUNT_SHIFT 3 +#define REFCOUNT_ONE (1<v & flag; +} + +INLINE uint32_t _upb_data_read_refcount(upb_data *d) { + if(upb_data_hasflag(d, UPB_DATA_FROZEN)) + data = upb_atomic_read(d); + else + data = data->val; + return (data & REFCOUNT_MASK) >> REFCOUNT_SHIFT; +} + +// Returns true if the given data has only one owner. +INLINE bool _upb_data_only(upb_data *data) { + return !upb_data_hasflag(data, UPB_DATA_REFCOUNTED) || + upb_data_read_refcount(data) == 1; +} // Specifies the type of ref that is requested based on the kind of access the // caller needs to the object. @@ -68,6 +103,30 @@ enum upb_ref_flags { UPB_REF_MUTABLE = 2 } +// Attempts to increment the reference on d with the given type of ref. If +// this is not possible, returns false. +INLINE bool upb_data_incref(upb_data *d, upb_reftype reftype) { + if((reftype == UPB_REF_FROZEN && !upb_data_hasflag(d, UPB_DATA_FROZEN)) || + (reftype == UPB_REF_MUTABLE && upb_data_hasflag(d, UPB_DATA_FROZEN)) || + !upb_data_hasflag(d, UPB_DATA_REFCOUNTED)) { + return false; + } + // Increment the ref. Only need to use atomic ops if the ref is frozen. + if(upb_data_hasflag(d, UPB_DATA_FROZEN)) upb_atomic_add(d, REFCOUNT_ONE); + else d->v += REFCOUNT_ONE; + return true; +} + +INLINE bool upb_data_decref(upb_data *d) { + if(upb_data_hasflag(d, UPB_DATA_FROZEN)) { + int32_t old_val = upb_atomic_fetch_and_add(d, -REFCOUNT_ONE); + return old_val & REFCOUNT_MASK == REFCOUNT_ONE; + } else { + *d -= REFCOUNT_ONE; + return *d & REFCOUNT_MASK == 0; + } +} + typedef uint8_t upb_flags_t; struct upb_mmhead {}; @@ -77,23 +136,35 @@ typedef uint32_t upb_strlen_t; // The members of this struct are private. Access should only be through the // associated functions. -typedef struct upb_string { - unsigned int byte_size:29; // How many bytes we own, 0 if we don't own. - bool is_heap_allocated:1; - bool is_frozen:1; - // TODO. At the moment, all dynamically allocated strings have refcounts. - bool has_refcount:1; +typedef struct { + upb_data base; upb_strlen_t byte_len; // We expect the data to be 8-bit clean (uint8_t), but char* is such an // ingrained convention that we follow it. char *ptr; -} upb_string; +} upb_string_common; + +typedef struct { + uint32_t byte_size_and_flags; + upb_strlen_t byte_len; + char *ptr; +} upb_norefcount_string; typedef struct { - upb_string s; - upb_atomic_refcount_t refcount; + upb_data base; + upb_strlen_t byte_len; + char *ptr; + uint32_t byte_size; } upb_refcounted_string; +typedef union { + upb_string_common common; + // Should only be accessed if flags indicate the string has *no* refcount. + upb_norefcount_string norefcount; + // Should only be accessed if flags indicate the string *has* a refcount. + upb_refcounted_string refcounted; +} upb_string; + // Returns a newly constructed string, which starts out empty. Caller owns one // ref on it. upb_string *upb_string_new(void); @@ -101,25 +172,15 @@ upb_string *upb_string_new(void); // Returns a string to which caller owns a ref, and contains the same contents // as src. The returned value may be a copy of src, if the requested flags // were incompatible with src's. -INLINE upb_string *upb_string_getref(upb_string *_s, upb_flags_t ref_flags) { - upb_refcount_string *s = _s; - if((ref_flags == UPB_REF_FROZEN && !s->is_frozen) || - (ref_flags == UPB_REF_MUTABLE && s->is_frozen) || - !s->has_refcount) { - // Copy should always be refcounted. Should be frozen iff a frozen ref was req. - return upb_strdup(s, flags); - } - // Take a ref on the existing object. - if(s->is_frozen) upb_atomic_ref(s->refcount); - else s->refcount.val++; - return s; +INLINE upb_string *upb_string_getref(upb_string *s, upb_flags_t ref_flags) { + if(upb_data_incref(&s->common.base, ref_flags)) return s; + return upb_strdup(s); } // The caller releases a ref on src, which it must previously have owned a ref // on. INLINE void upb_string_unref(upb_string *s) { - void *refcount = s + 1; - if(s->is_frozen) { + if(upb_data_unref(&s->common.base)) _upb_string_free(s); } // Returns a buffer to which the caller may write. The string is resized to @@ -130,12 +191,12 @@ char *upb_string_getrwbuf(upb_string *s, upb_strlen_t byte_len); // Returns a buffer that the caller may use to read the current contents of // the string. The number of bytes available is upb_strlen(s). INLINE const char *upb_string_getrobuf(upb_string *s) { - return s->ptr; + return s->common.ptr; } // Returns the current length of the string. INLINE size_t upb_strlen(upb_string *s) { - return s->byte_len; + return s->common.byte_len; } /* upb_string library functions ***********************************************/