e7ea5d10b3 — curl

Subject

base64: optimize decode lookup table and quantum loop

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Architecture & Compiler Flags

Architecture: x86_64-linux-gnu Compiler: gcc (Ubuntu 11.4.0-1ubuntu1~22.04.3) 11.4.0

—

Build Log

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Commit Diff GitHub →

lib/curlx/base64.c +46 -26

lib/curlx/base64.c+46 -26

@@ -37,12 +37,39 @@ const char curlx_base64encdec[] =
	static const char base64url[] =
	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";

-	static const unsigned char decodetable[] = {
-	62, 255, 255, 255, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 255,
-	255, 255, 255, 255, 255, 255, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
-	10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,
-	255, 255, 255, 255, 255, 255, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35,
-	36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51
+	static const unsigned char decodetable[256] = {
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 62, 0xff, 0xff, 0xff, 63,
+	52, 53, 54, 55, 56, 57, 58, 59,
+	60, 61, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0, 1, 2, 3, 4, 5, 6,
+	7, 8, 9, 10, 11, 12, 13, 14,
+	15, 16, 17, 18, 19, 20, 21, 22,
+	23, 24, 25, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 26, 27, 28, 29, 30, 31, 32,
+	33, 34, 35, 36, 37, 38, 39, 40,
+	41, 42, 43, 44, 45, 46, 47, 48,
+	49, 50, 51, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff
	};
	/*
	* curlx_base64_decode()
@@ -69,7 +96,6 @@ CURLcode curlx_base64_decode(const char *src,
	size_t rawlen = 0;
	unsigned char *pos;
	unsigned char *newstr;
-	unsigned char lookup[256];

	*outptr = NULL;
	*outlen = 0;
@@ -102,25 +128,19 @@ CURLcode curlx_base64_decode(const char *src,

	pos = newstr;

-	memset(lookup, 0xff, sizeof(lookup));
-	memcpy(&lookup['+'], decodetable, sizeof(decodetable));
-
	/* Decode the complete quantums first */
	for(i = 0; i < fullQuantums; i++) {
-	unsigned char val;
-	unsigned int x = 0;
-	int j;
-
-	for(j = 0; j < 4; j++) {
-	val = lookup[(unsigned char)*src++];
-	if(val == 0xff) /* bad symbol */
-	goto bad;
-	x = (x << 6) \| val;
-	}
-	pos[2] = x & 0xff;
-	pos[1] = (x >> 8) & 0xff;
-	pos[0] = (x >> 16) & 0xff;
+	unsigned char v0 = decodetable[(unsigned char)src[0]];
+	unsigned char v1 = decodetable[(unsigned char)src[1]];
+	unsigned char v2 = decodetable[(unsigned char)src[2]];
+	unsigned char v3 = decodetable[(unsigned char)src[3]];
+	if((v0 \| v1 \| v2 \| v3) & 0x80)
+	goto bad;
+	pos[0] = (unsigned char)((v0 << 2) \| (v1 >> 4));
+	pos[1] = (unsigned char)((v1 << 4) \| (v2 >> 2));
+	pos[2] = (unsigned char)((v2 << 6) \| v3);
	pos += 3;
+	src += 4;
	}
	if(padding) {
	/* this means either 8 or 16 bits output */
@@ -137,15 +157,15 @@ CURLcode curlx_base64_decode(const char *src,
	goto bad;
	}
	else {
-	val = lookup[(unsigned char)*src++];
+	val = decodetable[(unsigned char)*src++];
	if(val == 0xff) /* bad symbol */
	goto bad;
	x = (x << 6) \| val;
	}
	}
	if(padding == 1)
-	pos[1] = (x >> 8) & 0xff;
-	pos[0] = (x >> 16) & 0xff;
+	pos[1] = (unsigned char)((x >> 8) & 0xff);
+	pos[0] = (unsigned char)((x >> 16) & 0xff);
	pos += 3 - padding;
	}