From 673a363d4b4ba533130be5415fa7c9262347cf06 Mon Sep 17 00:00:00 2001
From: bumbread <thebumboni@gmail.com>
Date: Fri, 24 Jun 2022 12:24:04 +1100
Subject: [PATCH] uchar.h

---
 src/code/uchar.c | 136 +++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 131 insertions(+), 5 deletions(-)

diff --git a/src/code/uchar.c b/src/code/uchar.c
index 7bfc528..78bf4ac 100644
--- a/src/code/uchar.c
+++ b/src/code/uchar.c
@@ -9,6 +9,7 @@ size_t mbrtoc16(
     mbstate_t  *restrict ps
 ) {
     if(s == NULL) {
+        *ps = (mbstate_t) {0};
         return 0;
     }
     size_t nbytes;
@@ -49,8 +50,8 @@ size_t mbrtoc16(
         }
         else {
             cp -= 0x10000;
-            parsed_char = 0xd800 | (cp & 0x3ff);
-            next_char   = 0xdc00 | (cp >> 10);
+            parsed_char = 0xd800 | (cp >> 10);
+            next_char   = 0xdc00 | (cp & 0x3ff);
         }
     }
     else {
@@ -73,17 +74,142 @@ size_t c16rtomb(
     char *restrict      s,
     char16_t            c16,
     mbstate_t *restrict ps
-);
+) {
+    if(*s == NULL) {
+        *ps = (mbstate_t) {0};
+        return 0;
+    }
+    unsigned cp;
+    // High surrogate (save)
+    if(0xd800 <= c16 && c16 < 0xdc00) {
+        ps->leftover = c16;
+        return 0;
+    }
+    // Low surrogate (parse)
+    else if(0xdc00 <= c16 && c16 < 0xe000) {
+        if(ps->leftover == 0) goto encoding_error;
+        cp = ((ps->leftover & 0x3ff) << 10) | (c16 & 0x3ff);
+    }
+    // Other char
+    else {
+        cp = c16;
+    }
+    size_t nbytes = 4;
+    if(cp < 0x10000) nbytes = 3;
+    if(cp < 0x800)   nbytes = 2;
+    if(cp < 0x80)    nbytes = 1;
+    switch(nbytes) {
+        case 1: {
+            s[0] = cp;
+        } break;
+        case 2: {
+            s[0] = 0xc0 | (cp >> 6);
+            s[1] = 0x80 | ((cp >> 0)  & 0x3f);
+        } break;
+        case 3: {
+            s[0] = 0xe0 | (cp >> 12);
+            s[1] = 0x80 | ((cp >> 6)  & 0x3f);
+            s[2] = 0x80 | ((cp >> 0)  & 0x3f);
+        } break;
+        case 4: {
+            s[0] = 0xf0 | (cp >> 18);
+            s[1] = 0x80 | ((cp >> 12) & 0x3f);
+            s[2] = 0x80 | ((cp >> 6)  & 0x3f);
+            s[3] = 0x80 | ((cp >> 0)  & 0x3f);
+        } break;
+    }
+    return nbytes;
+encoding_error:
+    errno = EILSEQ;
+    return (size_t)(-1);
+}
 
 size_t mbrtoc32(
     char32_t   *restrict pc32,
     char const *restrict s,
     size_t               n,
     mbstate_t  *restrict ps
-);
+) {
+    if(s == NULL) {
+        *ps = (mbstate_t) {0};
+        return 0;
+    }
+    size_t nbytes;
+    
+    // Decode the first byte of UTF-8 sequence
+    unsigned byte0 = *s;
+    if     (0x00 <= byte0 && byte0 < 0x80) nbytes = 1;
+    else if(0xc0 <= byte0 && byte0 < 0xe0) nbytes = 2;
+    else if(0xe0 <= byte0 && byte0 < 0xf0) nbytes = 3;
+    else if(0xf0 <= byte0 && byte0 < 0xf8) nbytes = 4;
+    else goto encoding_error;
+    unsigned nbytesreq = nbytes;
+    if(n < nbytesreq) {
+        return (size_t)(-2);
+    }
+    char32_t cp = byte0;
+    switch(nbytesreq) {
+        case 2: cp &= 0x1f; break;
+        case 3: cp &= 0x0f; break;
+        case 4: cp &= 0x07; break;
+    }
+    while(--nbytesreq)
+        cp |= (cp << 6) | ((*++s) & 0x3f);
+    if(0xdc00 <= cp && cp <= 0xe000)
+        goto encoding_error;
+    // Overloing seqs
+    if(cp < 0x80    && nbytes > 1) goto encoding_error;
+    if(cp < 0x800   && nbytes > 2) goto encoding_error;
+    if(cp < 0x10000 && nbytes > 3) goto encoding_error;
+    if(cp > 0x10ffff) goto encoding_error;
+    
+    if(pc32 != NULL) *pc32 = cp;
+    if(cp == 0)
+        return 0;
+    else
+        return nbytes;
+encoding_error:
+    errno = EILSEQ;
+    return (size_t)(-1);
+}
 
 size_t c32rtomb(
     char *restrict      s,
     char32_t            c32,
     mbstate_t *restrict ps
-);
+) {
+    if(*s == NULL) {
+        *ps = (mbstate_t) {0};
+        return 0;
+    }
+    unsigned cp = c32;
+    if(cp >= 0x10ffff) goto encoding_error;
+    size_t nbytes = 4;
+    if(cp < 0x10000) nbytes = 3;
+    if(cp < 0x800)   nbytes = 2;
+    if(cp < 0x80)    nbytes = 1;
+    switch(nbytes) {
+        case 1: {
+            s[0] = cp;
+        } break;
+        case 2: {
+            s[0] = 0xc0 | (cp >> 6);
+            s[1] = 0x80 | ((cp >> 0)  & 0x3f);
+        } break;
+        case 3: {
+            s[0] = 0xe0 | (cp >> 12);
+            s[1] = 0x80 | ((cp >> 6)  & 0x3f);
+            s[2] = 0x80 | ((cp >> 0)  & 0x3f);
+        } break;
+        case 4: {
+            s[0] = 0xf0 | (cp >> 18);
+            s[1] = 0x80 | ((cp >> 12) & 0x3f);
+            s[2] = 0x80 | ((cp >> 6)  & 0x3f);
+            s[3] = 0x80 | ((cp >> 0)  & 0x3f);
+        } break;
+    }
+    return nbytes;
+encoding_error:
+    errno = EILSEQ;
+    return (size_t)(-1);
+}