diff options
Diffstat (limited to 'upb/pb/varint.h')
| -rw-r--r-- | upb/pb/varint.h | 88 |
1 files changed, 24 insertions, 64 deletions
diff --git a/upb/pb/varint.h b/upb/pb/varint.h index c0e0134..c4d67ba 100644 --- a/upb/pb/varint.h +++ b/upb/pb/varint.h @@ -49,71 +49,32 @@ typedef struct { uint64_t val; } upb_decoderet; -// A basic branch-based decoder, uses 32-bit values to get good performance -// on 32-bit architectures (but performs well on 64-bits also). -INLINE upb_decoderet upb_vdecode_branch32(const char *p) { - upb_decoderet r = {NULL, 0}; - uint32_t low, high = 0; - uint32_t b; - b = *(p++); low = (b & 0x7f) ; if(!(b & 0x80)) goto done; - b = *(p++); low |= (b & 0x7f) << 7; if(!(b & 0x80)) goto done; - b = *(p++); low |= (b & 0x7f) << 14; if(!(b & 0x80)) goto done; - b = *(p++); low |= (b & 0x7f) << 21; if(!(b & 0x80)) goto done; - b = *(p++); low |= (b & 0x7f) << 28; - high = (b & 0x7f) >> 4; if(!(b & 0x80)) goto done; - b = *(p++); high |= (b & 0x7f) << 3; if(!(b & 0x80)) goto done; - b = *(p++); high |= (b & 0x7f) << 10; if(!(b & 0x80)) goto done; - b = *(p++); high |= (b & 0x7f) << 17; if(!(b & 0x80)) goto done; - b = *(p++); high |= (b & 0x7f) << 24; if(!(b & 0x80)) goto done; - b = *(p++); high |= (b & 0x7f) << 31; if(!(b & 0x80)) goto done; - return r; - -done: - r.val = ((uint64_t)high << 32) | low; - r.p = p; - return r; -} - -// Like the previous, but uses 64-bit values. -INLINE upb_decoderet upb_vdecode_branch64(const char *p) { - uint64_t val; - uint64_t b; - upb_decoderet r = {NULL, 0}; - b = *(p++); val = (b & 0x7f) ; if(!(b & 0x80)) goto done; - b = *(p++); val |= (b & 0x7f) << 7; if(!(b & 0x80)) goto done; - b = *(p++); val |= (b & 0x7f) << 14; if(!(b & 0x80)) goto done; - b = *(p++); val |= (b & 0x7f) << 21; if(!(b & 0x80)) goto done; - b = *(p++); val |= (b & 0x7f) << 28; if(!(b & 0x80)) goto done; - b = *(p++); val |= (b & 0x7f) << 35; if(!(b & 0x80)) goto done; - b = *(p++); val |= (b & 0x7f) << 42; if(!(b & 0x80)) goto done; - b = *(p++); val |= (b & 0x7f) << 49; if(!(b & 0x80)) goto done; - b = *(p++); val |= (b & 0x7f) << 56; if(!(b & 0x80)) goto done; - b = *(p++); val |= (b & 0x7f) << 63; if(!(b & 0x80)) goto done; - return r; - -done: - r.val = val; - r.p = p; - return r; -} - -// Decodes a varint of at most 8 bytes without branching (except for error). +// Four functions for decoding a varint of at most eight bytes. They are all +// functionally identical, but are implemented in different ways and likely have +// different performance profiles. We keep them around for performance testing. +// +// Note that these functions may not read byte-by-byte, so they must not be used +// unless there are at least eight bytes left in the buffer! +upb_decoderet upb_vdecode_max8_branch32(upb_decoderet r); +upb_decoderet upb_vdecode_max8_branch64(upb_decoderet r); upb_decoderet upb_vdecode_max8_wright(upb_decoderet r); - -// Another implementation of the previous. upb_decoderet upb_vdecode_max8_massimino(upb_decoderet r); // Template for a function that checks the first two bytes with branching -// and dispatches 2-10 bytes with a separate function. -#define UPB_VARINT_DECODER_CHECK2(name, decode_max8_function) \ -INLINE upb_decoderet upb_vdecode_check2_ ## name(const char *_p) { \ - uint8_t *p = (uint8_t*)_p; \ - if ((*p & 0x80) == 0) { upb_decoderet r = {_p + 1, *p & 0x7f}; return r; } \ - upb_decoderet r = {_p + 2, (*p & 0x7f) | ((*(p + 1) & 0x7f) << 7)}; \ - if ((*(p + 1) & 0x80) == 0) return r; \ - return decode_max8_function(r); \ +// and dispatches 2-10 bytes with a separate function. Note that this may read +// up to 10 bytes, so it must not be used unless there are at least ten bytes +// left in the buffer! +#define UPB_VARINT_DECODER_CHECK2(name, decode_max8_function) \ +INLINE upb_decoderet upb_vdecode_check2_ ## name(const char *_p) { \ + uint8_t *p = (uint8_t*)_p; \ + if ((*p & 0x80) == 0) { upb_decoderet r = {_p + 1, *p & 0x7fU}; return r; } \ + upb_decoderet r = {_p + 2, (*p & 0x7fU) | ((*(p + 1) & 0x7fU) << 7)}; \ + if ((*(p + 1) & 0x80) == 0) return r; \ + return decode_max8_function(r); \ } +UPB_VARINT_DECODER_CHECK2(branch32, upb_vdecode_max8_branch32); +UPB_VARINT_DECODER_CHECK2(branch64, upb_vdecode_max8_branch64); UPB_VARINT_DECODER_CHECK2(wright, upb_vdecode_max8_wright); UPB_VARINT_DECODER_CHECK2(massimino, upb_vdecode_max8_massimino); #undef UPB_VARINT_DECODER_CHECK2 @@ -121,11 +82,10 @@ UPB_VARINT_DECODER_CHECK2(massimino, upb_vdecode_max8_massimino); // Our canonical functions for decoding varints, based on the currently // favored best-performing implementations. INLINE upb_decoderet upb_vdecode_fast(const char *p) { - // Use nobranch2 on 64-bit, branch32 on 32-bit. if (sizeof(long) == 8) return upb_vdecode_check2_massimino(p); else - return upb_vdecode_branch32(p); + return upb_vdecode_check2_branch32(p); } INLINE upb_decoderet upb_vdecode_max8_fast(upb_decoderet r) { @@ -154,9 +114,9 @@ INLINE size_t upb_vencode64(uint64_t val, char *buf) { if (val == 0) { buf[0] = 0; return 1; } size_t i = 0; while (val) { - uint8_t byte = val & 0x7f; + uint8_t byte = val & 0x7fU; val >>= 7; - if (val) byte |= 0x80; + if (val) byte |= 0x80U; buf[i++] = byte; } return i; @@ -169,7 +129,7 @@ INLINE uint64_t upb_vencode32(uint32_t val) { uint64_t ret = 0; assert(bytes <= 5); memcpy(&ret, buf, bytes); - assert(ret <= 0xffffffffff); + assert(ret <= 0xffffffffffU); return ret; } |