WebSVN – HelenOS – Diff – /trunk/kernel/generic/src/lib/string.c

 #define HI_MASK_8(n) (~LO_MASK_8(8 - (n)))
 /** Number of data bits in a UTF-8 continuation byte. */
 #define CONT_BITS 6
-/** Decode a single UTF-8 character from a NULL-terminated string.
+/** Decode a single character from a substring.
+ *
- * Decode a single UTF-8 character from a plain char NULL-terminated
+ * Decode a single character from a substring of size @a sz. Decoding starts
- * string. Decoding starts at @index and this index is moved to the
+ * at @a offset and this offset is moved to the beginning of the next
- * beginning of the next character. In case of decoding error,
+ * character. In case of decoding error, offset generally advances at least
- * index advances. However, index is never moved beyond (str+limit).
+ * by one. However, offset is never moved beyond (str + sz).
+ *
- * @param str   Plain character NULL-terminated string.
+ * @param str   String (not necessarily NULL-terminated).
  * @param index Index (counted in plain characters) where to start
  *              the decoding.
- * @param limit Maximal allowed value of index.
+ * @param limit Size of the substring.
+ *
- * @return Decoded character in UTF-32 or '?' if the encoding is wrong.
+ * @return  Value of decoded character or '?' on decoding error.
+ *
  */
-wchar_t utf8_decode(const char *str, index_t *index, index_t limit)
+wchar_t chr_decode(const char *str, size_t *offset, size_t sz)
+{
     uint8_t b0, b;          /* Bytes read from str. */
     wchar_t ch;
     int b0_bits;        /* Data bits in first byte. */
     int cbytes;     /* Number of continuation bytes. */
-    if (*index + 1 > limit)
+    if (*offset + 1 > sz)
         return invalch;
-    b0 = (uint8_t) str[(*index)++];
+    b0 = (uint8_t) str[(*offset)++];
     /* Determine code length. */
     if ((b0 & 0x80) == 0) {
         /* 0xxxxxxx (Plain ASCII) */
     } else {
         /* 10xxxxxx -- unexpected continuation byte. */
         return invalch;
+    }
-    if (*index + cbytes > limit) {
+    if (*offset + cbytes > sz) {
         return invalch;
+    }
     ch = b0 & LO_MASK_8(b0_bits);
     /* Decode continuation bytes. */
     while (cbytes > 0) {
-        b = (uint8_t) str[(*index)++];
+        b = (uint8_t) str[(*offset)++];
         /* Must be 10xxxxxx. */
         if ((b & 0xc0) != 0x80) {
             return invalch;
+        }
+    }
     return ch;
+}
-/** Encode a single UTF-32 character as UTF-8
- *
- * Encode a single UTF-32 character as UTF-8 and store it into
+/** Encode a single character to string representation.
- * the given buffer at @index. Encoding starts at @index and
- * this index is moved at the position where the next character
- * can be written to.
- *
- * @param ch    Input UTF-32 character.
- * @param str   Output buffer.
- * @param index Index (counted in plain characters) where to start
- *              the encoding
- * @param limit Maximal allowed value of index.
- *
- * @return True if the character was encoded or false if there is not
- *         enought space in the output buffer or the character is invalid
- *         Unicode code point.
+ *
+ * Encode a single character to string representation (i.e. UTF-8) and store
+ * it into a buffer at @a offset. Encoding starts at @a offset and this offset
+ * is moved to the position where the next character can be written to.
+ *
+ * @param ch        Input character.
+ * @param str       Output buffer.
+ * @param offset    Offset (in bytes) where to start writing.
+ * @param sz        Size of the output buffer.
+ *
+ * @return True if the character was encoded successfully or false if there
+ *     was not enough space in the output buffer or the character code
+ *     was invalid.
  */
-bool utf8_encode(const wchar_t ch, char *str, index_t *index, index_t limit)
+bool chr_encode(const wchar_t ch, char *str, size_t *offset, size_t sz)
+{
     uint32_t cc;        /* Unsigned version of ch. */
     int cbytes;     /* Number of continuation bytes. */
     int b0_bits;        /* Number of data bits in first byte. */
     int i;
-    if (*index >= limit)
+    if (*offset >= sz)
         return false;
     if (ch < 0)
         return false;
         /* Codes longer than 21 bits are not supported. */
         return false;
+    }
     /* Check for available space in buffer. */
-    if (*index + cbytes >= limit)
+    if (*offset + cbytes >= sz)
         return false;
     /* Encode continuation bytes. */
     for (i = cbytes; i > 0; --i) {
-        str[*index + i] = 0x80 | (cc & LO_MASK_32(CONT_BITS));
+        str[*offset + i] = 0x80 | (cc & LO_MASK_32(CONT_BITS));
         cc = cc >> CONT_BITS;
+    }
     /* Encode first byte. */
-    str[*index] = (cc & LO_MASK_32(b0_bits)) | HI_MASK_8(8 - b0_bits - 1);
+    str[*offset] = (cc & LO_MASK_32(b0_bits)) | HI_MASK_8(8 - b0_bits - 1);
-    /* Advance index. */
+    /* Advance offset. */
-    *index += (1 + cbytes);
+    *offset += (1 + cbytes);
     return true;
+}
 /** Get bytes used by UTF-8 characters.
     while (true) {
         iprev = index;
         if (size >= count)
             break;
-        ch = utf8_decode(str, &index, UTF8_NO_LIMIT);
+        ch = chr_decode(str, &index, UTF8_NO_LIMIT);
         if (ch == '\0') break;
         size++;
+    }
 size_t strlen_utf8(const char *str)
+{
     size_t size = 0;
     index_t index = 0;
-    while (utf8_decode(str, &index, UTF8_NO_LIMIT) != 0) {
+    while (chr_decode(str, &index, UTF8_NO_LIMIT) != 0) {
         size++;
+    }
     return size;
+}

Subversion Repositories HelenOS

(root)/trunk/kernel/generic/src/lib/string.c – Rev 4199 → 4200