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

  * @{
  */
 /**
  * @file
- * @brief Miscellaneous functions.
+ * @brief String functions.
+ *
+ * Strings and characters use the Universal Character Set (UCS). The standard
+ * strings, called just strings are encoded in UTF-8. Wide strings (encoded
+ * in UTF-32) are supported to a limited degree. A single character is
+ * represented as wchar_t.
+ *
+ * Strings have the following metrics:
+ *
+ *  Metric  Abbrev. Meaning
+ *  ------  ------  -------
+ *  size    n   Number of bytes the string is encoded into, excluding
+ *          the null terminator.
+ *  length  l   The number of characters in the string, excluding
+ *          the null terminator.
+ *  width   w   The number of character cells the string takes up on a
+ *          monospace display.
+ *
+ * Naming scheme:
+ *
+ *  chr_xxx     operate on characters
+ *  str_xxx     operate on strings
+ *  wstr_xxx    operate on wide strings
+ *
+ *  [w]str_[n|l|w]xxx   operate on a prefix limited by size, length
+ *              or width.
  */
 #include <string.h>
 #include <print.h>
 #include <cpu.h>
+ *
  * @return EOK if the character was encoded successfully, EOVERFLOW if there
  *     was not enough space in the output buffer or EINVAL if the character
  *     code was invalid.
  */
-int chr_encode(const wchar_t ch, char *str, size_t *offset, size_t sz)
+int chr_encode(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. */
     *offset += (1 + cbytes);
     return EOK;
+}
+/** Get display width of character.
+ *
+ * @param ch    The character.
+ * @return  Character width in display cells.
+ */
+count_t chr_width(wchar_t ch)
+{
+    return 1;
+}
 /** Get size of string, with length limit.
+ *
  * Get the number of bytes which are used by up to @a max_len first
  * characters in the string @a str. If @a max_len is greater than
  * the length of @a str, the entire string is measured.
+ *
  * @param str   String to consider.
  * @param count Maximum number of characters to measure.
+ *
- * @return Number of bytes used by the characters.
+ * @return  Number of bytes used by the characters.
  */
 size_t str_lsize(const char *str, count_t max_len)
+{
     count_t len = 0;
     size_t cur = 0;
+    }
     return prev;
+}
+/** Get size of string, with width limit.
+ *
+ * Get the number of bytes which are used by the longest prefix of @a str
+ * that can fit into @a max_width display cells.
+ *
+ * @param str   String to consider.
+ * @param count Maximum number of display cells.
+ *
+ * @return  Number of bytes used by the characters that fit.
+ */
+size_t str_wsize(const char *str, count_t max_width)
+{
+    count_t width = 0;
+    size_t cur = 0;
+    size_t prev;
+    wchar_t ch;
+    while (true) {
+        prev = cur;
+        if (width >= max_width)
+            break;
+        ch = chr_decode(str, &cur, UTF8_NO_LIMIT);
+        if (ch == '\0') break;
+        width += chr_width(ch);
+    }
+    return prev;
+}
+/** Get length of wide string, with width limit.
+ *
+ * Get the number of characters in a wide string that can fit into @a max_width
+ * display cells.
+ *
+ * @param wstr   Wide string to consider.
+ * @param count Maximum number of display cells.
+ *
+ * @return  Number of bytes used by the characters that fit.
+ */
+count_t wstr_wlength(const wchar_t *wstr, count_t max_width)
+{
+    count_t width = 0;
+    index_t cur = 0;
+    while (true) {
+        if (width >= max_width)
+            break;
+        if (wstr[cur] == '\0') break;
+        width += chr_width(wstr[cur]);
+        ++cur;
+    }
+    return (count_t) cur;
+}
 /** Check whether character is plain ASCII.
+ *
  * @return True if character is plain ASCII.
+ *
  */
     return len;
+}
 /** Return number of characters in a wide string.
+ *
- * @param str NULL-terminated wide string.
+ * @param   str NULL-terminated wide string.
- * @return Number of characters in @a str.
+ * @return  Number of characters in @a str.
  */
 count_t wstr_length(const wchar_t *wstr)
+{
     count_t len;

Subversion Repositories HelenOS

(root)/trunk/kernel/generic/src/lib/string.c – Rev 4208 → 4209