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mruby-pack: optimize quoted-printable format with ascii fast path and lookup tables

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Co-authored-by: Claude <noreply@anthropic.com>
This commit is contained in:
Yukihiro "Matz" Matsumoto
2025-08-14 14:44:15 +09:00
parent 433328bbbb
commit 43cf4c32ca
1 changed files with 96 additions and 34 deletions
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mrbgems/mruby-pack/src/pack.c
+96 -34
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@@ -229,6 +229,32 @@ static const uint8_t utf8_is_continuation[128] = {
/* Helper macro for continuation byte validation */
#define IS_UTF8_CONTINUATION(byte) \
((byte) >= 0x80 && utf8_is_continuation[(byte) - 0x80])
/* Quoted-printable optimization lookup table */
/* 0=literal, 1=encode, 2=special (newline) */
static const uint8_t qprint_encode_type[256] = {
/* 0x00-0x1F: Control characters - encode */
1,1,1,1,1,1,1,1, 1,0,2,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
/* \t \n */
/* 0x20-0x3F: Printable ASCII */
0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,1,0,0,
/* = */
/* 0x40-0x5F: Printable ASCII */
0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,
/* 0x60-0x7F: Printable ASCII */
0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,1,
/* DEL*/
/* 0x80-0xFF: High-bit characters - encode */
1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1
};
/* template parsing optimization structures */
typedef struct {
enum pack_dir dir;
@@ -1286,36 +1312,57 @@ pack_qenc(mrb_state *mrb, mrb_value src, mrb_value dst, mrb_int didx, int count)
int dlen = 0;
if (count <= 1) count = 72;
while (s < send) {
if ((*s > 126) ||
(*s < 32 && *s != '\n' && *s != '\t') ||
(*s == '=')) {
unsigned char byte = (unsigned char)*s;
uint8_t encode_type = qprint_encode_type[byte];
/* ASCII printable fast path - most common case */
if (encode_type == 0) {
/* Handle space/tab at line end special case */
if ((byte == ' ' || byte == '\t') && s + 1 < send && *(s + 1) == '\n') {
/* Space/tab before newline needs encoding */
buff[i++] = '=';
buff[i++] = hex_table[(byte & 0xf0) >> 4];
buff[i++] = hex_table[byte & 0x0f];
n += 3;
prev = EOF;
}
else {
/* Regular printable character - direct copy */
buff[i++] = byte;
n++;
prev = byte;
}
}
/* Newline special handling */
else if (encode_type == 2) {
if (prev == ' ' || prev == '\t') {
buff[i++] = '=';
buff[i++] = byte;
}
buff[i++] = byte;
n = 0;
prev = byte;
}
/* Character needs encoding */
else {
buff[i++] = '=';
buff[i++] = hex_table[(*s & 0xf0) >> 4];
buff[i++] = hex_table[*s & 0x0f];
buff[i++] = hex_table[(byte & 0xf0) >> 4];
buff[i++] = hex_table[byte & 0x0f];
n += 3;
prev = EOF;
}
else if (*s == '\n') {
if (prev == ' ' || prev == '\t') {
buff[i++] = '=';
buff[i++] = *s;
}
buff[i++] = *s;
n = 0;
prev = *s;
}
else {
buff[i++] = *s;
n++;
prev = *s;
}
/* Check line length limit */
if (n > count) {
buff[i++] = '=';
buff[i++] = '\n';
n = 0;
prev = '\n';
}
/* Flush buffer if getting full */
if (i > 1024 - 5) {
str_len_ensure(mrb, dst, didx+dlen+i);
memcpy(RSTRING_PTR(dst)+didx+dlen, buff, i);
@@ -1324,15 +1371,20 @@ pack_qenc(mrb_state *mrb, mrb_value src, mrb_value dst, mrb_int didx, int count)
}
s++;
}
/* Add final soft line break if needed */
if (n > 0) {
buff[i++] = '=';
buff[i++] = '\n';
}
/* Flush remaining buffer */
if (i > 0) {
str_len_ensure(mrb, dst, didx+dlen+i);
memcpy(RSTRING_PTR(dst)+didx+dlen, buff, i);
dlen += i;
}
return dlen;
}
@@ -1342,31 +1394,41 @@ unpack_qenc(mrb_state *mrb, const void *src, int slen, mrb_value ary)
CHECK_UNPACK_LEN(mrb, slen, ary);
mrb_value buf = mrb_str_new(mrb, 0, slen);
const char *s = (const char*)src, *ss = s;
const char *s = (const char*)src;
const char *send = s + slen;
char *ptr = RSTRING_PTR(buf);
int c1, c2;
while (s < send) {
if (*s == '=') {
if (++s == send) break;
if (s+1 < send && *s == '\r' && *(s+1) == '\n')
s++;
if (*s != '\n') {
if ((c1 = hex2int(*s)) == -1) break;
if (++s == send) break;
if ((c2 = hex2int(*s)) == -1) break;
*ptr++ = (char)(c1 << 4 | c2);
}
}
else {
/* Fast path for non-encoded characters - most common case */
if (*s != '=') {
*ptr++ = *s;
s++;
continue;
}
/* Handle =XX encoded sequences */
if (++s == send) break;
/* Handle soft line breaks: =\r\n or =\n */
if (s + 1 < send && *s == '\r' && *(s + 1) == '\n') {
s += 2; /* Skip \r\n */
continue;
}
if (*s == '\n') {
s++; /* Skip \n */
continue;
}
/* Decode =XX hex sequence */
if ((c1 = hex2int(*s)) == -1) break;
if (++s == send) break;
if ((c2 = hex2int(*s)) == -1) break;
*ptr++ = (char)(c1 << 4 | c2);
s++;
ss = s;
}
buf = mrb_str_resize(mrb, buf, (mrb_int)(ptr - RSTRING_PTR(buf)));
mrb_str_cat(mrb, buf, ss, send-ss);
mrb_ary_push(mrb, ary, buf);
return slen;
}