From 60f21f065f9cb8ec3bfba035d7e1ed2e3ee87d49 Mon Sep 17 00:00:00 2001
From: Miccah <m.castorina93@gmail.com>
Date: Sun, 15 Aug 2021 20:59:21 -0500
Subject: [PATCH] encoding.hex: remove strconv dependency (#11196)

---
 vlib/encoding/hex/hex.v      | 48 +++++++++++++++++++++++++++---------
 vlib/encoding/hex/hex_test.v | 13 ++++++++++
 2 files changed, 49 insertions(+), 12 deletions(-)

diff --git a/vlib/encoding/hex/hex.v b/vlib/encoding/hex/hex.v
index 6f75f2fff6..99387f15e7 100644
--- a/vlib/encoding/hex/hex.v
+++ b/vlib/encoding/hex/hex.v
@@ -1,25 +1,39 @@
 module hex
 
-import strconv
 import strings
 
 // decode converts a hex string into an array of bytes. The expected
 // input format is 2 ASCII characters for each output byte. If the provided
 // string length is not a multiple of 2, an implicit `0` is prepended to it.
 pub fn decode(s string) ?[]byte {
-	if s.len == 0 {
-		return []byte{}
-	} else if s.len <= 2 {
-		return [byte(strconv.parse_uint(s, 16, 8) ?)]
+	mut hex_str := s
+	if hex_str.len >= 2 {
+		if s[0] == `0` && (s[1] == `x` || s[1] == `X`) {
+			hex_str = s[2..]
+		}
 	}
-	// calculate the first byte depending on if s.len is odd
-	val := byte(strconv.parse_uint(s[..2 - (s.len & 1)], 16, 8) ?)
-	// set cap to s.len/2 rounded up
-	mut bytes := []byte{len: 1, cap: (s.len + 1) >> 1, init: val}
+	if hex_str.len == 0 {
+		return []byte{}
+	} else if hex_str.len == 1 {
+		return [char2nibble(hex_str[0]) ?]
+	} else if hex_str.len == 2 {
+		n1 := char2nibble(hex_str[0]) ?
+		n0 := char2nibble(hex_str[1]) ?
+		return [(n1 << 4) | n0]
+	}
+	// calculate the first byte depending on if hex_str.len is odd
+	mut val := char2nibble(hex_str[0]) ?
+	if hex_str.len & 1 == 0 {
+		val = (val << 4) | char2nibble(hex_str[1]) ?
+	}
+	// set cap to hex_str.len/2 rounded up
+	mut bytes := []byte{len: 1, cap: (hex_str.len + 1) >> 1, init: val}
 	// iterate over every 2 bytes
-	// the start index depends on if s.len is odd
-	for i := 2 - (s.len & 1); i < s.len; i += 2 {
-		bytes << byte(strconv.parse_uint(s[i..i + 2], 16, 8) ?)
+	// the start index depends on if hex_str.len is odd
+	for i := 2 - (hex_str.len & 1); i < hex_str.len; i += 2 {
+		n1 := char2nibble(hex_str[i]) ?
+		n0 := char2nibble(hex_str[i + 1]) ?
+		bytes << (n1 << 4) | n0
 	}
 	return bytes
 }
@@ -36,3 +50,13 @@ pub fn encode(bytes []byte) string {
 	unsafe { sb.free() }
 	return res
 }
+
+// char2nibble converts an ASCII hex character to it's hex value
+fn char2nibble(b byte) ?byte {
+	match b {
+		`0`...`9` { return b - byte(`0`) }
+		`A`...`F` { return b - byte(`A`) + 10 }
+		`a`...`f` { return b - byte(`a`) + 10 }
+		else { return error('invalid hex char $b.ascii_str()') }
+	}
+}
diff --git a/vlib/encoding/hex/hex_test.v b/vlib/encoding/hex/hex_test.v
index 1be8f80e7e..62501e9ded 100644
--- a/vlib/encoding/hex/hex_test.v
+++ b/vlib/encoding/hex/hex_test.v
@@ -9,6 +9,8 @@ fn test_decode() ? {
 	assert decode('123') ? == [byte(0x1), 0x23]
 	assert decode('1234') ? == [byte(0x12), 0x34]
 	assert decode('12345') ? == [byte(0x1), 0x23, 0x45]
+	assert decode('0123456789abcdef') ? == [byte(0x01), 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef]
+	assert decode('123456789ABCDEF') ? == [byte(0x01), 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef]
 }
 
 fn test_decode_fails() ? {
@@ -38,4 +40,15 @@ fn test_encode() ? {
 	assert encode(decode('123') ?) == '0123'
 	assert encode(decode('1234') ?) == '1234'
 	assert encode(decode('12345') ?) == '012345'
+	assert encode(decode('abcdef') ?) == 'abcdef'
+	assert encode(decode('ABCDEF') ?) == 'abcdef'
+}
+
+fn test_decode_0x() ? {
+	assert decode('0x') ? == []
+	assert decode('0x0') ? == [byte(0x0)]
+	assert decode('0X1234') ? == [byte(0x12), 0x34]
+	assert decode('0x12345') ? == [byte(0x1), 0x23, 0x45]
+	assert decode('0x0123456789abcdef') ? == [byte(0x01), 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef]
+	assert decode('0X123456789ABCDEF') ? == [byte(0x01), 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef]
 }