From d0600f57146b36afdd279964c7e72f31cb9ee9a5 Mon Sep 17 00:00:00 2001
From: apio <blobs.trading@gmail.com>
Date: Sat, 14 Jan 2023 12:07:08 +0100
Subject: [PATCH] luna: Make Utf8StringEncoder short-circuit instead of failing
 when hitting the length limit

---
 luna/src/Utf8.cpp | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/luna/src/Utf8.cpp b/luna/src/Utf8.cpp
index 269efdbd..9c9ea7ad 100644
--- a/luna/src/Utf8.cpp
+++ b/luna/src/Utf8.cpp
@@ -2,8 +2,6 @@
 #include <luna/CString.h>
 #include <luna/Utf8.h>
 
-// FIXME: Not enough space for a sequence is not an error. (mbstowcs(3) and wcstombs(3), case 2 when buf is not NULL)
-
 static_assert(WCHAR_MAX > 0x10ffff);
 
 static Result<usize> utf8_char_length(char c)
@@ -32,31 +30,31 @@ static inline usize wide_char_length_as_utf8_unchecked(wchar_t c)
     return 4;
 }
 
-static Result<void> encode_wide_char_as_utf8(wchar_t c, char* result, usize& len)
+static Result<bool> encode_wide_char_as_utf8(wchar_t c, char* result, usize& len)
 {
     const usize utf8_len = TRY(wide_char_length_as_utf8(c));
 
-    if (utf8_len > len) { return err(EILSEQ); }
+    if (utf8_len > len) { return false; } // Not enough space
 
     u8* buf = (u8*)result;
 
     if (len == 1)
     {
         buf[0] = c & 0x7f;
-        return {};
+        return true;
     }
     if (len == 2)
     {
         buf[0] = 0b11000000 | ((c & 0x7c0) >> 6);
         buf[1] = 0b10000000 | (c & 0x3f);
-        return {};
+        return true;
     }
     if (len == 3)
     {
         buf[0] = 0b11100000 | ((c & 0xf000) >> 12);
         buf[1] = 0b10000000 | ((c & 0xfc0) >> 6);
         buf[2] = 0b10000000 | (c & 0x3f);
-        return {};
+        return true;
     }
     if (len == 4)
     {
@@ -64,7 +62,7 @@ static Result<void> encode_wide_char_as_utf8(wchar_t c, char* result, usize& len
         buf[1] = 0b10000000 | ((c & 0x3f000) >> 12);
         buf[2] = 0b10000000 | ((c & 0xfc0) >> 6);
         buf[3] = 0b10000000 | (c & 0x3f);
-        return {};
+        return true;
     }
 
     unreachable();
@@ -197,7 +195,8 @@ Result<usize> Utf8StringEncoder::encode(char* buf, usize max) const
     while (*it && max > 1)
     {
         usize len = max - 1;
-        TRY(encode_wide_char_as_utf8(*it, buf, len));
+        bool ok = TRY(encode_wide_char_as_utf8(*it, buf, len));
+        if (!ok) break;
         buf += len;
         max -= len;
         it++;