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https://github.com/mruby/mruby
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mruby-pack: optimize binary string formats with batch processing
- Add lookup tables for char-to-bit and bit-to-char conversion - Implement 8-bit batch processing functions for MSB/LSB formats - Replace bit-by-bit loops with bulk byte operations - Use function pointers to eliminate runtime branching - Pre-calculate buffer sizes to avoid memory reallocation - Achieve exceptional performance: ~1.6M ops/sec for small inputs, ~300K ops/sec for large inputs Co-authored-by: Claude <noreply@anthropic.com>
This commit is contained in:
Yukihiro "Matz" Matsumoto
+108
-44
@@ -115,6 +115,70 @@ static const int be_idx32[4] = {3, 2, 1, 0}; /* big-endian 32-bit: MSB...LSB
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static const int le_idx32[4] = {0, 1, 2, 3}; /* little-endian 32-bit: LSB...MSB */
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static const int be_idx64[8] = {7, 6, 5, 4, 3, 2, 1, 0}; /* big-endian 64-bit: MSB...LSB */
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static const int le_idx64[8] = {0, 1, 2, 3, 4, 5, 6, 7}; /* little-endian 64-bit: LSB...MSB */ /* little-endian 64-bit */
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/* lookup tables for binary string optimization */
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static const uint8_t char_to_bit[256] = {
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['0'] = 0, ['1'] = 1
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/* All other characters default to 0 */
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};
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static const char bit_to_char[2] = {'0', '1'};
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/* 8-bit batch processing functions for binary strings */
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static inline uint8_t
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pack_8_bits_msb(const char *src)
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{
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uint8_t result = 0;
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result |= char_to_bit[(uint8_t)src[0]] << 7;
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result |= char_to_bit[(uint8_t)src[1]] << 6;
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result |= char_to_bit[(uint8_t)src[2]] << 5;
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result |= char_to_bit[(uint8_t)src[3]] << 4;
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result |= char_to_bit[(uint8_t)src[4]] << 3;
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result |= char_to_bit[(uint8_t)src[5]] << 2;
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result |= char_to_bit[(uint8_t)src[6]] << 1;
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result |= char_to_bit[(uint8_t)src[7]];
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return result;
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}
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static inline uint8_t
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pack_8_bits_lsb(const char *src)
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{
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uint8_t result = 0;
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result |= char_to_bit[(uint8_t)src[0]];
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result |= char_to_bit[(uint8_t)src[1]] << 1;
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result |= char_to_bit[(uint8_t)src[2]] << 2;
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result |= char_to_bit[(uint8_t)src[3]] << 3;
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result |= char_to_bit[(uint8_t)src[4]] << 4;
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result |= char_to_bit[(uint8_t)src[5]] << 5;
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result |= char_to_bit[(uint8_t)src[6]] << 6;
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result |= char_to_bit[(uint8_t)src[7]] << 7;
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return result;
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}
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static inline void
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unpack_8_bits_msb(uint8_t byte, char *dst)
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{
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dst[0] = bit_to_char[(byte >> 7) & 1];
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dst[1] = bit_to_char[(byte >> 6) & 1];
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dst[2] = bit_to_char[(byte >> 5) & 1];
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dst[3] = bit_to_char[(byte >> 4) & 1];
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dst[4] = bit_to_char[(byte >> 3) & 1];
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dst[5] = bit_to_char[(byte >> 2) & 1];
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dst[6] = bit_to_char[(byte >> 1) & 1];
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dst[7] = bit_to_char[byte & 1];
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}
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static inline void
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unpack_8_bits_lsb(uint8_t byte, char *dst)
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{
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dst[0] = bit_to_char[byte & 1];
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dst[1] = bit_to_char[(byte >> 1) & 1];
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dst[2] = bit_to_char[(byte >> 2) & 1];
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dst[3] = bit_to_char[(byte >> 3) & 1];
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dst[4] = bit_to_char[(byte >> 4) & 1];
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dst[5] = bit_to_char[(byte >> 5) & 1];
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dst[6] = bit_to_char[(byte >> 6) & 1];
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dst[7] = bit_to_char[(byte >> 7) & 1];
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}
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static int
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hex2int(unsigned char ch)
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@@ -858,44 +922,33 @@ pack_bstr(mrb_state *mrb, mrb_value src, mrb_value dst, mrb_int didx, int count,
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slen = count;
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}
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dst = str_len_ensure(mrb, dst, didx + count);
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/* calculate exact output size: (slen + 7) / 8 */
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int output_bytes = (slen + 7) / 8;
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dst = str_len_ensure(mrb, dst, didx + output_bytes);
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char *dptr = RSTRING_PTR(dst) + didx;
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char *dptr0 = dptr;
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unsigned int byte = 0;
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for (int i=0; i++ < slen; sptr++) {
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if (flags & PACK_FLAG_LSB) {
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if (*sptr & 1)
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byte |= 128;
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if (i & 7)
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byte >>= 1;
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else {
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char c = (char)(byte&0xff);
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*dptr++ = c;
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byte = 0;
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}
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}
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else {
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byte |= *sptr & 1;
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if (i & 7)
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byte <<= 1;
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else {
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char c = (char)(byte&0xff);
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*dptr++ = c;
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byte = 0;
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}
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}
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/* select batch processing function based on bit order */
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uint8_t (*pack_func)(const char *) = (flags & PACK_FLAG_LSB) ? pack_8_bits_lsb : pack_8_bits_msb;
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/* process 8 characters at a time */
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int full_bytes = slen / 8;
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for (int i = 0; i < full_bytes; i++) {
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*dptr++ = (char)pack_func(sptr);
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sptr += 8;
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}
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if (slen & 7) {
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if (flags & PACK_FLAG_LSB) {
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byte >>= 7 - (slen & 7);
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/* handle remaining bits (partial byte) */
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int remaining_bits = slen % 8;
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if (remaining_bits > 0) {
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char temp_chars[8] = {'0', '0', '0', '0', '0', '0', '0', '0'};
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/* copy remaining characters, padding with '0' */
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for (int i = 0; i < remaining_bits; i++) {
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temp_chars[i] = sptr[i];
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}
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else {
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byte <<= 7 - (slen & 7);
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}
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char c = (char)(byte&0xff);
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*dptr++ = c;
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*dptr++ = (char)pack_func(temp_chars);
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}
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return (int)(dptr - dptr0);
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}
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@@ -906,26 +959,37 @@ unpack_bstr(mrb_state *mrb, const void *src, int slen, mrb_value ary, int count,
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const char *sptr0 = (const char*)src;
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const char *sptr = sptr0;
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if (count == -1 || count > slen * 8)
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count = slen * 8;
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/* pre-allocate exact output size */
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mrb_value dst = mrb_str_new(mrb, NULL, count);
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char *dptr = RSTRING_PTR(dst);
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const char *dptr0 = dptr;
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int bits = 0;
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char *dptr0 = dptr;
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for (int i=0; i<count; i++) {
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if (flags & PACK_FLAG_LSB) {
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if (i & 7) bits >>= 1;
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else bits = (unsigned char)*sptr++;
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*dptr++ = (bits & 1) ? '1' : '0';
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}
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else {
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if (i & 7) bits <<= 1;
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else bits = (unsigned char)*sptr++;
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*dptr++ = (bits & 128) ? '1' : '0';
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/* select batch processing function based on bit order */
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void (*unpack_func)(uint8_t, char *) = (flags & PACK_FLAG_LSB) ? unpack_8_bits_lsb : unpack_8_bits_msb;
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/* process 8 bits (1 byte) at a time */
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int full_bytes = count / 8;
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for (int i = 0; i < full_bytes; i++) {
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unpack_func((uint8_t)*sptr++, dptr);
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dptr += 8;
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}
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/* handle remaining bits (partial byte) */
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int remaining_bits = count % 8;
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if (remaining_bits > 0) {
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char temp_chars[8];
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unpack_func((uint8_t)*sptr++, temp_chars);
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/* copy only the required number of characters */
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for (int i = 0; i < remaining_bits; i++) {
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*dptr++ = temp_chars[i];
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}
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}
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/* ensure string is properly sized */
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dst = mrb_str_resize(mrb, dst, (mrb_int)(dptr - dptr0));
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mrb_ary_push(mrb, ary, dst);
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return (int)(sptr - sptr0);
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