From: compmaniak <6314398+compmaniak@users.noreply.github.com>
Date: Wed, 30 Aug 2017 22:59:22 +0000 (+0300)
Subject: lib: Preallocate output space for base64 encoding
X-Git-Tag: 2.3.0.rc1~1119
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4e3be303f875ae203c6dec74b967ce868561851e;p=thirdparty%2Fdovecot%2Fcore.git

lib: Preallocate output space for base64 encoding
---

diff --git a/src/lib/base64.c b/src/lib/base64.c
index d84014b7b2..ceaa1ff555 100644
--- a/src/lib/base64.c
+++ b/src/lib/base64.c
@@ -45,36 +45,38 @@ static const unsigned char b64dec[256] = {
 
 void base64_encode(const void *src, size_t src_size, buffer_t *dest)
 {
+	const size_t res_size = MAX_BASE64_ENCODED_SIZE(src_size);
+	unsigned char *start = buffer_append_space_unsafe(dest, res_size);
+	unsigned char *ptr = start;
 	const unsigned char *src_c = src;
-	unsigned char tmp[4];
 	size_t src_pos;
 
-	for (src_pos = 0; src_size - src_pos > 2; src_pos += 3) {
-		tmp[0] = b64enc[src_c[src_pos] >> 2];
-		tmp[1] = b64enc[((src_c[src_pos] & 0x03) << 4) |
+	for (src_pos = 0; src_size - src_pos > 2; src_pos += 3, ptr += 4) {
+		ptr[0] = b64enc[src_c[src_pos] >> 2];
+		ptr[1] = b64enc[((src_c[src_pos] & 0x03) << 4) |
 				(src_c[src_pos+1] >> 4)];
-		tmp[2] = b64enc[((src_c[src_pos+1] & 0x0f) << 2) |
+		ptr[2] = b64enc[((src_c[src_pos+1] & 0x0f) << 2) |
 				((src_c[src_pos+2] & 0xc0) >> 6)];
-		tmp[3] = b64enc[src_c[src_pos+2] & 0x3f];
-		buffer_append(dest, tmp, 4);
+		ptr[3] = b64enc[src_c[src_pos+2] & 0x3f];
 	}
+
+	i_assert(ptr <= start + res_size);
+
 	switch (src_size - src_pos) {
 	case 0:
 		break;
 	case 1:
-		tmp[0] = b64enc[src_c[src_pos] >> 2];
-		tmp[1] = b64enc[(src_c[src_pos] & 0x03) << 4];
-		tmp[2] = '=';
-		tmp[3] = '=';
-		buffer_append(dest, tmp, 4);
+		ptr[0] = b64enc[src_c[src_pos] >> 2];
+		ptr[1] = b64enc[(src_c[src_pos] & 0x03) << 4];
+		ptr[2] = '=';
+		ptr[3] = '=';
 		break;
 	case 2:
-		tmp[0] = b64enc[src_c[src_pos] >> 2];
-		tmp[1] = b64enc[((src_c[src_pos] & 0x03) << 4) |
+		ptr[0] = b64enc[src_c[src_pos] >> 2];
+		ptr[1] = b64enc[((src_c[src_pos] & 0x03) << 4) |
 				(src_c[src_pos+1] >> 4)];
-		tmp[2] = b64enc[((src_c[src_pos+1] & 0x0f) << 2)];
-		tmp[3] = '=';
-		buffer_append(dest, tmp, 4);
+		ptr[2] = b64enc[((src_c[src_pos+1] & 0x0f) << 2)];
+		ptr[3] = '=';
 		break;
 	default:
 		i_unreached();