From b772731b98256b45ef2362bbdb55085094cf3d02 Mon Sep 17 00:00:00 2001
From: Surman The Dead <70163032+SurmanPP@users.noreply.github.com>
Date: Sun, 9 Apr 2023 09:32:49 +0200
Subject: [PATCH] leb128: make decoding return the number of decoded bytes, in
 addition to the decoded value (#17912)

---
 vlib/encoding/leb128/leb128.v      | 24 ++++++++++++------------
 vlib/encoding/leb128/leb128_test.v | 16 ++++++++++++----
 2 files changed, 24 insertions(+), 16 deletions(-)

diff --git a/vlib/encoding/leb128/leb128.v b/vlib/encoding/leb128/leb128.v
index 587f939e8e..0c679d0bb0 100644
--- a/vlib/encoding/leb128/leb128.v
+++ b/vlib/encoding/leb128/leb128.v
@@ -66,8 +66,8 @@ pub fn encode_u32(value u32) []u8 {
 	return result
 }
 
-// decode_i32 decodes an i32 from the given leb128 encoded array `value`
-pub fn decode_i32(value []u8) i32 {
+// decode_i32 decodes an i32 and returns the number of bytes used from the given leb128 encoded array `value`
+pub fn decode_i32(value []u8) (i32, int) {
 	mut result := int(0)
 	mut shift := 0
 	for b in value {
@@ -80,11 +80,11 @@ pub fn decode_i32(value []u8) i32 {
 			break
 		}
 	}
-	return result
+	return result, shift / 7
 }
 
-// decode_i64 decodes an i64 from the given leb128 encoded array `value`
-pub fn decode_i64(value []u8) i64 {
+// decode_i64 decodes an i64 and returns the number of bytes used from the given leb128 encoded array `value`
+pub fn decode_i64(value []u8) (i64, int) {
 	mut result := u64(0)
 	mut shift := 0
 	for b in value {
@@ -97,11 +97,11 @@ pub fn decode_i64(value []u8) i64 {
 			break
 		}
 	}
-	return i64(result)
+	return i64(result), shift / 7
 }
 
-// decode_u64 decodes an u64 from the given leb128 encoded array `value`
-pub fn decode_u64(value []u8) u64 {
+// decode_u64 decodes an u64 and returns the number of bytes used from the given leb128 encoded array `value`
+pub fn decode_u64(value []u8) (u64, int) {
 	mut result := u64(0)
 	mut shift := 0
 	for b in value {
@@ -111,11 +111,11 @@ pub fn decode_u64(value []u8) u64 {
 		}
 		shift += 7
 	}
-	return result
+	return result, shift / 7 + 1
 }
 
-// decode_u32 decodes an u32 from the given leb128 encoded array `value`
-pub fn decode_u32(value []u8) u32 {
+// decode_u32 decodes an u32 and returns the number of bytes used from the given leb128 encoded array `value`
+pub fn decode_u32(value []u8) (u32, int) {
 	mut result := u32(0)
 	mut shift := 0
 	for b in value {
@@ -125,5 +125,5 @@ pub fn decode_u32(value []u8) u32 {
 		}
 		shift += 7
 	}
-	return result
+	return result, shift / 7 + 1
 }
diff --git a/vlib/encoding/leb128/leb128_test.v b/vlib/encoding/leb128/leb128_test.v
index ee6030be3b..b7ac828d8b 100644
--- a/vlib/encoding/leb128/leb128_test.v
+++ b/vlib/encoding/leb128/leb128_test.v
@@ -13,9 +13,13 @@ struct PairI {
 
 fn test_basic() {
 	assert leb128.encode_u64(624485) == [u8(0xe5), 0x8e, 0x26]
-	assert leb128.decode_u64([u8(0xe5), 0x8e, 0x26]) == 624485
+	uval, ulen := leb128.decode_u64([u8(0xe5), 0x8e, 0x26])
+	assert uval == 624485, 'val, _ := leb128.decode_u64([u8(0xe5), 0x8e, 0x26]) == 624486'
+	assert ulen == 3, '_, len := leb128.decode_u64([u8(0xe5), 0x8e, 0x26]) == 3'
 	assert leb128.encode_i64(-123456) == [u8(0xc0), 0xbb, 0x78]
-	assert leb128.decode_i64([u8(0xc0), 0xbb, 0x78]) == -123456
+	sval, slen := leb128.decode_i64([u8(0xc0), 0xbb, 0x78])
+	assert sval == -123456, 'val, _ := leb128.decode_i64([u8(0xc0), 0xbb, 0x78]) == -123456'
+	assert slen == 3, '_, len := leb128.decode_i64([u8(0xc0), 0xbb, 0x78]) == 3'
 }
 
 fn test_unsigned_data() {
@@ -23,7 +27,9 @@ fn test_unsigned_data() {
 		assert leb128.encode_u64(x.value).hex() == x.encoded, 'leb128.encode_u64( ${x.value} )  == ${x.encoded}'
 		bytes := hex.decode(x.encoded)!
 		// eprintln('>> bytes: ${bytes} | pair: ${x}')
-		assert leb128.decode_u64(bytes) == x.value, 'leb128.decode_u64( ${x.encoded} ) == ${x.value}'
+		val, len := leb128.decode_u64(bytes)
+		assert val == x.value, 'val, _ := leb128.decode_u64( ${x.encoded} ) == ${x.value}'
+		assert len == bytes.len, '_, len := leb128.decode_u64( ${x.encoded} ) = ${bytes.len}'
 	}
 }
 
@@ -32,7 +38,9 @@ fn test_signed_data() {
 		assert leb128.encode_i64(x.value).hex() == x.encoded, 'k: ${x.value} | v: ${x.encoded}'
 		bytes := hex.decode(x.encoded)!
 		// eprintln('>> bytes: ${bytes} | pair: ${x}')
-		assert leb128.decode_i64(bytes) == x.value, 'leb128.decode_i64( ${x.encoded} ) == ${x.value}'
+		val, len := leb128.decode_i64(bytes)
+		assert val == x.value, 'val, _ := leb128.decode_i64( ${x.encoded} ) == ${x.value}'
+		assert len == bytes.len, '_, len := leb128.decode_i64( ${x.encoded} ) == ${x.value}'
 	}
 }