From: shugo@... (MAEDA Shugo)
Date: 1998-12-09T19:23:20+09:00
Subject: [ruby-dev:3786] pack("m")

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前田です。

>>>>> In [ruby-dev:3773]
>>>>> "前田" == MAEDA Shugo <shugo@aianet.ne.jp> san wrote:

前田> pack.cのencodes()は、ループの中で毎回str_cat()を呼ぶために、
前田> 何度もreallocするせいで少し遅いような気がするのですが、どうでしょう。

バッファリングするようにしたらかなり速くなりました:-)

$ time /usr/local/bin/ruby -e '[open("ruby").read].pack("m")'
real    0m3.651s
user    0m2.400s
sys     0m1.250s
$ time ./ruby -e '[open("ruby").read].pack("m")'

real    0m0.891s
user    0m0.750s
sys     0m0.140s

パッチを添付します。
あと、文字列の範囲外のメモリにアクセスしないように変更してあります。


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--- pack.c.orig	Wed Dec  9 16:47:44 1998
+++ pack.c	Wed Dec  9 19:08:37 1998
@@ -513,38 +513,41 @@
     int len;
     int type;
 {
-    char hunk[4];
+    char *buff = ALLOCA_N(char, len * 4 / 3 + 6);
+    int i = 0;
     char *p, *pend;
     char *trans = type == 'u' ? uu_table : b64_table;
     int padding;
 
     if (type == 'u') {
-	*hunk = len + ' ';
-	str_cat(str, hunk, 1);
+	buff[i++] = len + ' ';
 	padding = '`';
     }
     else {
 	padding = '=';
     }
-    while (len > 0) {
-	hunk[0] = trans[077 & (*s >> 2)];
-	hunk[1] = trans[077 & (((*s << 4) & 060) | ((s[1] >> 4) & 017))];
-	hunk[2] = trans[077 & (((s[1] << 2) & 074) | ((s[2] >> 6) & 03))];
-	hunk[3] = trans[077 & s[2]];
-	str_cat(str, hunk, 4);
+    while (len >= 3) {
+	buff[i++] = trans[077 & (*s >> 2)];
+	buff[i++] = trans[077 & (((*s << 4) & 060) | ((s[1] >> 4) & 017))];
+	buff[i++] = trans[077 & (((s[1] << 2) & 074) | ((s[2] >> 6) & 03))];
+	buff[i++] = trans[077 & s[2]];
 	s += 3;
 	len -= 3;
     }
-    p = RSTRING(str)->ptr;
-    pend = RSTRING(str)->ptr + RSTRING(str)->len;
-    if (len == -1) {
-	pend[-1] = padding;
+    if (len == 2) {
+	buff[i++] = trans[077 & (*s >> 2)];
+	buff[i++] = trans[077 & (((*s << 4) & 060) | ((s[1] >> 4) & 017))];
+	buff[i++] = trans[077 & (((s[1] << 2) & 074) | (('\0' >> 6) & 03))];
+	buff[i++] = padding;
     }
-    else if (len == -2) {
-	pend[-2] = padding;
-	pend[-1] = padding;
+    else if (len == 1) {
+	buff[i++] = trans[077 & (*s >> 2)];
+	buff[i++] = trans[077 & (((*s << 4) & 060) | (('\0' >> 4) & 017))];
+	buff[i++] = padding;
+	buff[i++] = padding;
     }
-    str_cat(str, "\n", 1);
+    buff[i++] = '\n';
+    str_cat(str, buff, i);
 }
 
 static char hex_table[] = "0123456789ABCDEF";

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-- 
前田 修吾 (mailto:shugo@aianet.ne.jp)

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