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protobuf-c.c: Make zigzag encoding more compact

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Also match upstream code in src/google/protobuf/wire_format_lite.h
This commit is contained in:
Ilya Lipnitskiy 2019-10-17 17:22:19 -07:00
parent 9f89e64083
commit 66e8aa5ed3
1 changed files with 10 additions and 16 deletions
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26
protobuf-c/protobuf-c.c
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@ -312,10 +312,9 @@ int32_size(int32_t v)
static inline uint32_t
zigzag32(int32_t v)
{
if (v < 0)
return (-(uint32_t)v) * 2 - 1;
else
return (uint32_t)(v) * 2;
// Note: the right-shift must be arithmetic
// Note: left shift must be unsigned because of overflow
return ((uint32_t)(v) << 1) ^ (uint32_t)(v >> 31);
}
/**
@ -377,10 +376,9 @@ uint64_size(uint64_t v)
static inline uint64_t
zigzag64(int64_t v)
{
if (v < 0)
return (-(uint64_t)v) * 2 - 1;
else
return (uint64_t)(v) * 2;
// Note: the right-shift must be arithmetic
// Note: left shift must be unsigned because of overflow
return ((uint64_t)(v) << 1) ^ (uint64_t)(v >> 63);
}
/**
@ -2423,10 +2421,8 @@ parse_int32(unsigned len, const uint8_t *data)
static inline int32_t
unzigzag32(uint32_t v)
{
if (v & 1)
return -(v >> 1) - 1;
else
return v >> 1;
// Note: Using unsigned types prevents undefined behavior
return (int32_t)((v >> 1) ^ (~(v & 1) + 1));
}
static inline uint32_t
@ -2467,10 +2463,8 @@ parse_uint64(unsigned len, const uint8_t *data)
static inline int64_t
unzigzag64(uint64_t v)
{
if (v & 1)
return -(v >> 1) - 1;
else
return v >> 1;
// Note: Using unsigned types prevents undefined behavior
return (int64_t)((v >> 1) ^ (~(v & 1) + 1));
}
static inline uint64_t