From 9952519ec5270532e15c743ce3491ec4d0c3c488 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 28 Jan 2026 16:38:54 +0000
Subject: [PATCH 1/4] Initial plan


From e4f3e05cc0086f7a5d7d3b0c0df5a02279d43cbc Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 28 Jan 2026 16:48:18 +0000
Subject: [PATCH 2/4] Fix single-byte encoder validation for null chars and
 byte-0 mappings

Co-authored-by: ChALkeR <291301+ChALkeR@users.noreply.github.com>
---
 single-byte.js      | 4 ++--
 single-byte.node.js | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/single-byte.js b/single-byte.js
index 5462587e..5a5a7596 100644
--- a/single-byte.js
+++ b/single-byte.js
@@ -69,7 +69,7 @@ function encode(s, m) {
   for (const len3 = len - 3; i < len3; i += 4) {
     const x0 = s.charCodeAt(i), x1 = s.charCodeAt(i + 1), x2 = s.charCodeAt(i + 2), x3 = s.charCodeAt(i + 3) // prettier-ignore
     const c0 = m[x0], c1 = m[x1], c2 = m[x2], c3 = m[x3] // prettier-ignore
-    if ((!c0 && x0) || (!c1 && x1) || (!c2 && x2) || (!c3 && x3)) return null
+    if (c0 === undefined || c1 === undefined || c2 === undefined || c3 === undefined) return null
 
     x[i] = c0
     x[i + 1] = c1
@@ -80,7 +80,7 @@ function encode(s, m) {
   for (; i < len; i++) {
     const x0 = s.charCodeAt(i)
     const c0 = m[x0]
-    if (!c0 && x0) return null
+    if (c0 === undefined) return null
     x[i] = c0
   }
 
diff --git a/single-byte.node.js b/single-byte.node.js
index 2f68c9c2..9d02709b 100644
--- a/single-byte.node.js
+++ b/single-byte.node.js
@@ -70,7 +70,7 @@ function encode(s, m) {
   for (const len3 = len - 3; i < len3; i += 4) {
     const x0 = x[i], x1 = x[i + 1], x2 = x[i + 2], x3 = x[i + 3] // prettier-ignore
     const c0 = m[x0], c1 = m[x1], c2 = m[x2], c3 = m[x3] // prettier-ignore
-    if (!(c0 && c1 && c2 && c3) && ((!c0 && x0) || (!c1 && x1) || (!c2 && x2) || (!c3 && x3))) return null // prettier-ignore
+    if (c0 === undefined || c1 === undefined || c2 === undefined || c3 === undefined) return null
     x[i] = c0
     x[i + 1] = c1
     x[i + 2] = c2
@@ -80,7 +80,7 @@ function encode(s, m) {
   for (; i < len; i++) {
     const x0 = x[i]
     const c0 = m[x0]
-    if (!c0 && x0) return null
+    if (c0 === undefined) return null
     x[i] = c0
   }
 

From 87dde53fba8338583ae5c630119e27fb652a0397 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 28 Jan 2026 16:52:22 +0000
Subject: [PATCH 3/4] Add prettier-ignore comments for consistency

Co-authored-by: ChALkeR <291301+ChALkeR@users.noreply.github.com>
---
 single-byte.js      | 2 +-
 single-byte.node.js | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/single-byte.js b/single-byte.js
index 5a5a7596..2d9f7f35 100644
--- a/single-byte.js
+++ b/single-byte.js
@@ -69,7 +69,7 @@ function encode(s, m) {
   for (const len3 = len - 3; i < len3; i += 4) {
     const x0 = s.charCodeAt(i), x1 = s.charCodeAt(i + 1), x2 = s.charCodeAt(i + 2), x3 = s.charCodeAt(i + 3) // prettier-ignore
     const c0 = m[x0], c1 = m[x1], c2 = m[x2], c3 = m[x3] // prettier-ignore
-    if (c0 === undefined || c1 === undefined || c2 === undefined || c3 === undefined) return null
+    if (c0 === undefined || c1 === undefined || c2 === undefined || c3 === undefined) return null // prettier-ignore
 
     x[i] = c0
     x[i + 1] = c1
diff --git a/single-byte.node.js b/single-byte.node.js
index 9d02709b..21c0f201 100644
--- a/single-byte.node.js
+++ b/single-byte.node.js
@@ -70,7 +70,7 @@ function encode(s, m) {
   for (const len3 = len - 3; i < len3; i += 4) {
     const x0 = x[i], x1 = x[i + 1], x2 = x[i + 2], x3 = x[i + 3] // prettier-ignore
     const c0 = m[x0], c1 = m[x1], c2 = m[x2], c3 = m[x3] // prettier-ignore
-    if (c0 === undefined || c1 === undefined || c2 === undefined || c3 === undefined) return null
+    if (c0 === undefined || c1 === undefined || c2 === undefined || c3 === undefined) return null // prettier-ignore
     x[i] = c0
     x[i + 1] = c1
     x[i + 2] = c2

From 2542ebdbf01c011c7c21428b370a932a77cbb8a8 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 28 Jan 2026 17:10:29 +0000
Subject: [PATCH 4/4] Revert "Fix single-byte encoder validation" - original
 logic was correct

The original validation check (!c0 && x0) is correct and intentional:
- It detects when a non-zero character (x0 > 0) tries to map to byte 0
- This is important because in some encodings (windows-1250, windows-1252, x-user-defined),
  character U+0080 maps to byte 0, which should be rejected since byte 0 is reserved for null
- The check correctly allows charCode 0 to map to byte 0 since (!0 && 0) = false

My previous change broke this by only checking for undefined, which allowed non-zero
characters to incorrectly map to byte 0.

Co-authored-by: ChALkeR <291301+ChALkeR@users.noreply.github.com>
---
 single-byte.js      | 4 ++--
 single-byte.node.js | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/single-byte.js b/single-byte.js
index 2d9f7f35..5462587e 100644
--- a/single-byte.js
+++ b/single-byte.js
@@ -69,7 +69,7 @@ function encode(s, m) {
   for (const len3 = len - 3; i < len3; i += 4) {
     const x0 = s.charCodeAt(i), x1 = s.charCodeAt(i + 1), x2 = s.charCodeAt(i + 2), x3 = s.charCodeAt(i + 3) // prettier-ignore
     const c0 = m[x0], c1 = m[x1], c2 = m[x2], c3 = m[x3] // prettier-ignore
-    if (c0 === undefined || c1 === undefined || c2 === undefined || c3 === undefined) return null // prettier-ignore
+    if ((!c0 && x0) || (!c1 && x1) || (!c2 && x2) || (!c3 && x3)) return null
 
     x[i] = c0
     x[i + 1] = c1
@@ -80,7 +80,7 @@ function encode(s, m) {
   for (; i < len; i++) {
     const x0 = s.charCodeAt(i)
     const c0 = m[x0]
-    if (c0 === undefined) return null
+    if (!c0 && x0) return null
     x[i] = c0
   }
 
diff --git a/single-byte.node.js b/single-byte.node.js
index 21c0f201..2f68c9c2 100644
--- a/single-byte.node.js
+++ b/single-byte.node.js
@@ -70,7 +70,7 @@ function encode(s, m) {
   for (const len3 = len - 3; i < len3; i += 4) {
     const x0 = x[i], x1 = x[i + 1], x2 = x[i + 2], x3 = x[i + 3] // prettier-ignore
     const c0 = m[x0], c1 = m[x1], c2 = m[x2], c3 = m[x3] // prettier-ignore
-    if (c0 === undefined || c1 === undefined || c2 === undefined || c3 === undefined) return null // prettier-ignore
+    if (!(c0 && c1 && c2 && c3) && ((!c0 && x0) || (!c1 && x1) || (!c2 && x2) || (!c3 && x3))) return null // prettier-ignore
     x[i] = c0
     x[i + 1] = c1
     x[i + 2] = c2
@@ -80,7 +80,7 @@ function encode(s, m) {
   for (; i < len; i++) {
     const x0 = x[i]
     const c0 = m[x0]
-    if (c0 === undefined) return null
+    if (!c0 && x0) return null
     x[i] = c0
   }