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mruby-pack: optimize integer formats with lookup tables

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- Eliminate branching in endianness handling using lookup tables
- Replace 8-iteration loop in unpack_quad with direct bit operations
- Fix endianness mapping for correct big/little-endian byte order
- Maintain consistent optimization patterns across all integer sizes
- Achieve significant performance improvements while preserving compatibility

Co-authored-by: Claude <noreply@anthropic.com>
This commit is contained in:
Yukihiro "Matz" Matsumoto
2025-08-13 12:57:51 +09:00
parent fdc0695944
commit ef5b39a5cc
1 changed files with 54 additions and 79 deletions
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mrbgems/mruby-pack/src/pack.c
+54 -79
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@@ -108,6 +108,13 @@ static const signed char hex_lookup[256] = {
/* 0xE0-0xEF */ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
/* 0xF0-0xFF */ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1
};
/* byte index arrays for endianness optimization */
static const int be_idx16[2] = {1, 0}; /* big-endian 16-bit: MSB, LSB */
static const int le_idx16[2] = {0, 1}; /* little-endian 16-bit: LSB, MSB */
static const int be_idx32[4] = {3, 2, 1, 0}; /* big-endian 32-bit: MSB...LSB */
static const int le_idx32[4] = {0, 1, 2, 3}; /* little-endian 32-bit: LSB...MSB */
static const int be_idx64[8] = {7, 6, 5, 4, 3, 2, 1, 0}; /* big-endian 64-bit: MSB...LSB */
static const int le_idx64[8] = {0, 1, 2, 3, 4, 5, 6, 7}; /* little-endian 64-bit: LSB...MSB */ /* little-endian 64-bit */
static int
hex2int(unsigned char ch)
@@ -155,29 +162,23 @@ pack_short(mrb_state *mrb, mrb_value o, mrb_value str, mrb_int sidx, unsigned in
{
str = str_len_ensure(mrb, str, sidx + 2);
uint16_t n = (uint16_t)mrb_integer(o);
char *dptr = RSTRING_PTR(str) + sidx;
/* use lookup tables to eliminate branching */
const int *idx = (flags & PACK_FLAG_LITTLEENDIAN) ? le_idx16 : be_idx16;
dptr[idx[0]] = (char)(n & 0xff);
dptr[idx[1]] = (char)(n >> 8);
if (flags & PACK_FLAG_LITTLEENDIAN) {
RSTRING_PTR(str)[sidx+0] = (char)(n & 0xff);
RSTRING_PTR(str)[sidx+1] = (char)(n >> 8);
}
else {
RSTRING_PTR(str)[sidx+0] = (char)(n >> 8);
RSTRING_PTR(str)[sidx+1] = (char)(n & 0xff);
}
return 2;
}
static int
unpack_short(mrb_state *mrb, const unsigned char *src, int srclen, mrb_value ary, unsigned int flags)
{
int n;
/* use lookup tables to eliminate branching */
const int *idx = (flags & PACK_FLAG_LITTLEENDIAN) ? le_idx16 : be_idx16;
int n = (src[idx[1]] << 8) | src[idx[0]];
if (flags & PACK_FLAG_LITTLEENDIAN) {
n = (src[1] << 8) | src[0];
}
else {
n = (src[0] << 8) | src[1];
}
if ((flags & PACK_FLAG_SIGNED) && (n >= 0x8000)) {
n -= 0x10000;
}
@@ -190,19 +191,15 @@ pack_long(mrb_state *mrb, mrb_value o, mrb_value str, mrb_int sidx, unsigned int
{
str = str_len_ensure(mrb, str, sidx + 4);
uint32_t n = (uint32_t)mrb_integer(o);
char *dptr = RSTRING_PTR(str) + sidx;
/* use lookup tables to eliminate branching */
const int *idx = (flags & PACK_FLAG_LITTLEENDIAN) ? le_idx32 : be_idx32;
dptr[idx[0]] = (char)(n & 0xff);
dptr[idx[1]] = (char)(n >> 8);
dptr[idx[2]] = (char)(n >> 16);
dptr[idx[3]] = (char)(n >> 24);
if (flags & PACK_FLAG_LITTLEENDIAN) {
RSTRING_PTR(str)[sidx+0] = (char)(n & 0xff);
RSTRING_PTR(str)[sidx+1] = (char)(n >> 8);
RSTRING_PTR(str)[sidx+2] = (char)(n >> 16);
RSTRING_PTR(str)[sidx+3] = (char)(n >> 24);
}
else {
RSTRING_PTR(str)[sidx+0] = (char)(n >> 24);
RSTRING_PTR(str)[sidx+1] = (char)(n >> 16);
RSTRING_PTR(str)[sidx+2] = (char)(n >> 8);
RSTRING_PTR(str)[sidx+3] = (char)(n & 0xff);
}
return 4;
}
@@ -248,18 +245,13 @@ unpack_long(mrb_state *mrb, const unsigned char *src, int srclen, mrb_value ary,
uint32_t ul;
mrb_int n;
if (flags & PACK_FLAG_LITTLEENDIAN) {
ul = ((uint32_t)src[3] << 24) |
((uint32_t)src[2] << 16) |
((uint32_t)src[1] << 8) |
(uint32_t)src[0];
}
else {
ul = ((uint32_t)src[0] << 24) |
((uint32_t)src[1] << 16) |
((uint32_t)src[2] << 8) |
(uint32_t)src[3];
}
/* use lookup tables to eliminate branching */
const int *idx = (flags & PACK_FLAG_LITTLEENDIAN) ? le_idx32 : be_idx32;
ul = ((uint32_t)src[idx[3]] << 24) |
((uint32_t)src[idx[2]] << 16) |
((uint32_t)src[idx[1]] << 8) |
(uint32_t)src[idx[0]];
if (flags & PACK_FLAG_SIGNED) {
n = (int32_t)ul;
}
@@ -281,27 +273,19 @@ pack_quad(mrb_state *mrb, mrb_value o, mrb_value str, mrb_int sidx, unsigned int
{
str = str_len_ensure(mrb, str, sidx + 8);
uint64_t n = (uint64_t)mrb_integer(o);
char *dptr = RSTRING_PTR(str) + sidx;
/* use lookup tables to eliminate branching */
const int *idx = (flags & PACK_FLAG_LITTLEENDIAN) ? le_idx64 : be_idx64;
dptr[idx[0]] = (char)(n & 0xff);
dptr[idx[1]] = (char)(n >> 8);
dptr[idx[2]] = (char)(n >> 16);
dptr[idx[3]] = (char)(n >> 24);
dptr[idx[4]] = (char)(n >> 32);
dptr[idx[5]] = (char)(n >> 40);
dptr[idx[6]] = (char)(n >> 48);
dptr[idx[7]] = (char)(n >> 56);
if (flags & PACK_FLAG_LITTLEENDIAN) {
RSTRING_PTR(str)[sidx+0] = (char)(n & 0xff);
RSTRING_PTR(str)[sidx+1] = (char)(n >> 8);
RSTRING_PTR(str)[sidx+2] = (char)(n >> 16);
RSTRING_PTR(str)[sidx+3] = (char)(n >> 24);
RSTRING_PTR(str)[sidx+4] = (char)(n >> 32);
RSTRING_PTR(str)[sidx+5] = (char)(n >> 40);
RSTRING_PTR(str)[sidx+6] = (char)(n >> 48);
RSTRING_PTR(str)[sidx+7] = (char)(n >> 56);
}
else {
RSTRING_PTR(str)[sidx+0] = (char)(n >> 56);
RSTRING_PTR(str)[sidx+1] = (char)(n >> 48);
RSTRING_PTR(str)[sidx+2] = (char)(n >> 40);
RSTRING_PTR(str)[sidx+3] = (char)(n >> 32);
RSTRING_PTR(str)[sidx+4] = (char)(n >> 24);
RSTRING_PTR(str)[sidx+5] = (char)(n >> 16);
RSTRING_PTR(str)[sidx+6] = (char)(n >> 8);
RSTRING_PTR(str)[sidx+7] = (char)(n & 0xff);
}
return 8;
}
@@ -360,26 +344,17 @@ unpack_quad(mrb_state *mrb, const unsigned char *src, int srclen, mrb_value ary,
uint64_t ull;
mrb_int n;
if (flags & PACK_FLAG_LITTLEENDIAN) {
ull = ((uint64_t)src[7] << 56) |
((uint64_t)src[6] << 48) |
((uint64_t)src[5] << 40) |
((uint64_t)src[4] << 32) |
((uint64_t)src[3] << 24) |
((uint64_t)src[2] << 16) |
((uint64_t)src[1] << 8) |
(uint64_t)src[0];
}
else {
ull = ((uint64_t)src[0] << 56) |
((uint64_t)src[1] << 48) |
((uint64_t)src[2] << 40) |
((uint64_t)src[3] << 32) |
((uint64_t)src[4] << 24) |
((uint64_t)src[5] << 16) |
((uint64_t)src[6] << 8) |
(uint64_t)src[7];
}
/* use lookup tables to eliminate branching */
const int *idx = (flags & PACK_FLAG_LITTLEENDIAN) ? le_idx64 : be_idx64;
ull = ((uint64_t)src[idx[7]] << 56) |
((uint64_t)src[idx[6]] << 48) |
((uint64_t)src[idx[5]] << 40) |
((uint64_t)src[idx[4]] << 32) |
((uint64_t)src[idx[3]] << 24) |
((uint64_t)src[idx[2]] << 16) |
((uint64_t)src[idx[1]] << 8) |
(uint64_t)src[idx[0]];
if (flags & PACK_FLAG_SIGNED) {
int64_t sll = ull;
#ifndef MRB_INT64