From b373fb4a424119c314da7c8a62aa3811c6a4698c Mon Sep 17 00:00:00 2001
From: Matt Van Horn <455140+mvanhorn@users.noreply.github.com>
Date: Sun, 15 Mar 2026 21:20:45 -0700
Subject: [PATCH] Address review feedback: fix endless loop, use stdlib, add
charset flag
- Use std.ascii.eqlIgnoreCase instead of custom asciiEqlIgnoreCase
- Fix infinite loop in findAttrValue when attribute has no '=' sign
(e.g. self-closing )
- Add is_default_charset flag to Mime struct so prescan only overrides
charset when Content-Type header didn't set one explicitly
- Add regression test for the self-closing meta loop case
Co-Authored-By: Claude Opus 4.6
---
src/browser/Mime.zig | 35 +++++++++++++++++++----------------
src/browser/Page.zig | 4 ++--
2 files changed, 21 insertions(+), 18 deletions(-)
diff --git a/src/browser/Mime.zig b/src/browser/Mime.zig
index beef2177..13951259 100644
--- a/src/browser/Mime.zig
+++ b/src/browser/Mime.zig
@@ -25,6 +25,7 @@ params: []const u8 = "",
// We keep 41 for null-termination since HTML parser expects in this format.
charset: [41]u8 = default_charset,
charset_len: usize = default_charset_len,
+is_default_charset: bool = true,
/// String "UTF-8" continued by null characters.
const default_charset = .{ 'U', 'T', 'F', '-', '8' } ++ .{0} ** 36;
@@ -130,6 +131,7 @@ pub fn parse(input: []u8) !Mime {
var charset: [41]u8 = default_charset;
var charset_len: usize = default_charset_len;
+ var has_explicit_charset = false;
var it = std.mem.splitScalar(u8, params, ';');
while (it.next()) |attr| {
@@ -156,6 +158,7 @@ pub fn parse(input: []u8) !Mime {
// Null-terminate right after attribute value.
charset[attribute_value.len] = 0;
charset_len = attribute_value.len;
+ has_explicit_charset = true;
},
}
}
@@ -165,6 +168,7 @@ pub fn parse(input: []u8) !Mime {
.charset = charset,
.charset_len = charset_len,
.content_type = content_type,
+ .is_default_charset = !has_explicit_charset,
};
}
@@ -212,7 +216,7 @@ pub fn prescanCharset(html: []const u8) ?[]const u8 {
// Look for http-equiv="content-type" with content="...;charset=X"
if (findAttrValue(attrs, "http-equiv")) |he| {
- if (asciiEqlIgnoreCase(he, "content-type")) {
+ if (std.ascii.eqlIgnoreCase(he, "content-type")) {
if (findAttrValue(attrs, "content")) |content| {
if (extractCharsetFromContentType(content)) |charset| {
return charset;
@@ -248,7 +252,11 @@ fn findAttrValue(attrs: []const u8, name: []const u8) ?[]const u8 {
// Skip whitespace around =
while (pos < attrs.len and (attrs[pos] == ' ' or attrs[pos] == '\t')) pos += 1;
- if (pos >= attrs.len or attrs[pos] != '=') continue;
+ if (pos >= attrs.len or attrs[pos] != '=') {
+ // No '=' found - skip this token. Advance at least one byte to avoid infinite loop.
+ if (pos == attr_start) pos += 1;
+ continue;
+ }
pos += 1; // skip '='
while (pos < attrs.len and (attrs[pos] == ' ' or attrs[pos] == '\t')) pos += 1;
if (pos >= attrs.len) return null;
@@ -274,7 +282,7 @@ fn findAttrValue(attrs: []const u8, name: []const u8) ?[]const u8 {
}
};
- if (asciiEqlIgnoreCase(attr_name, name)) return value;
+ if (std.ascii.eqlIgnoreCase(attr_name, name)) return value;
}
return null;
}
@@ -283,7 +291,7 @@ fn extractCharsetFromContentType(content: []const u8) ?[]const u8 {
var it = std.mem.splitScalar(u8, content, ';');
while (it.next()) |part| {
const trimmed = std.mem.trimLeft(u8, part, &.{ ' ', '\t' });
- if (trimmed.len > 8 and asciiEqlIgnoreCase(trimmed[0..8], "charset=")) {
+ if (trimmed.len > 8 and std.ascii.eqlIgnoreCase(trimmed[0..8], "charset=")) {
const val = std.mem.trim(u8, trimmed[8..], &.{ ' ', '\t', '"', '\'' });
if (val.len > 0 and val.len <= 40) return val;
}
@@ -291,14 +299,6 @@ fn extractCharsetFromContentType(content: []const u8) ?[]const u8 {
return null;
}
-fn asciiEqlIgnoreCase(a: []const u8, b: []const u8) bool {
- if (a.len != b.len) return false;
- for (a, b) |ca, cb| {
- if (std.ascii.toLower(ca) != std.ascii.toLower(cb)) return false;
- }
- return true;
-}
-
pub fn sniff(body: []const u8) ?Mime {
// 0x0C is form feed
const content = std.mem.trimLeft(u8, body, &.{ ' ', '\t', '\n', '\r', 0x0C });
@@ -725,14 +725,17 @@ test "Mime: prescanCharset" {
);
// No charset found
- try testing.expectEqual(@as(?[]const u8, null), Mime.prescanCharset("Test"));
- try testing.expectEqual(@as(?[]const u8, null), Mime.prescanCharset(""));
- try testing.expectEqual(@as(?[]const u8, null), Mime.prescanCharset("no html here"));
+ try testing.expectEqual(null, Mime.prescanCharset("Test"));
+ try testing.expectEqual(null, Mime.prescanCharset(""));
+ try testing.expectEqual(null, Mime.prescanCharset("no html here"));
+
+ // Self-closing meta without charset must not loop forever
+ try testing.expectEqual(null, Mime.prescanCharset(""));
// Charset after 1024 bytes should not be found
var long_html: [1100]u8 = undefined;
@memset(&long_html, ' ');
const suffix = "";
@memcpy(long_html[1050 .. 1050 + suffix.len], suffix);
- try testing.expectEqual(@as(?[]const u8, null), Mime.prescanCharset(&long_html));
+ try testing.expectEqual(null, Mime.prescanCharset(&long_html));
}
diff --git a/src/browser/Page.zig b/src/browser/Page.zig
index ab291bc6..9f7a22a1 100644
--- a/src/browser/Page.zig
+++ b/src/browser/Page.zig
@@ -855,9 +855,9 @@ fn pageDataCallback(transfer: *HttpClient.Transfer, data: []const u8) !void {
break :blk Mime.sniff(data);
} orelse .unknown;
- // If the HTTP header didn't specify a charset and this is HTML,
+ // If the HTTP Content-Type header didn't specify a charset and this is HTML,
// prescan the first 1024 bytes for a declaration.
- if (mime.content_type == .text_html and std.mem.eql(u8, mime.charsetString(), "UTF-8")) {
+ if (mime.content_type == .text_html and mime.is_default_charset) {
if (Mime.prescanCharset(data)) |charset| {
if (charset.len <= 40) {
@memcpy(mime.charset[0..charset.len], charset);