1 /***************************************************************************
2 * Copyright (c) 2024 Microsoft Corporation
3 *
4 * This program and the accompanying materials are made available under the
5 * terms of the MIT License which is available at
6 * https://opensource.org/licenses/MIT.
7 *
8 * SPDX-License-Identifier: MIT
9 **************************************************************************/
10
11
12 /**************************************************************************/
13 /**************************************************************************/
14 /** */
15 /** GUIX Component */
16 /** */
17 /** Utility (Utility) */
18 /** */
19 /**************************************************************************/
20
21 #define GX_SOURCE_CODE
22
23 /* Include necessary system files. */
24
25 #include "gx_api.h"
26 #include "gx_utility.h"
27
28 /**************************************************************************/
29 /* */
30 /* FUNCTION RELEASE */
31 /* */
32 /* _gx_utility_utf8_string_backward_character_length_get */
33 /* PORTABLE C */
34 /* 6.1 */
35 /* AUTHOR */
36 /* */
37 /* Kenneth Maxwell, Microsoft Corporation */
38 /* */
39 /* DESCRIPTION */
40 /* */
41 /* This function returns the glyph length of the previous character */
42 /* from the specified byte position. */
43 /* */
44 /* INPUT */
45 /* */
46 /* string UTF-8 string */
47 /* start_index Specified byte position */
48 /* glyph_len Length of glyph value in byte */
49 /* */
50 /* OUTPUT */
51 /* */
52 /* status Completion status */
53 /* */
54 /* CALLS */
55 /* */
56 /* */
57 /* CALLED BY */
58 /* */
59 /* GUIX Internal Code */
60 /* */
61 /* RELEASE HISTORY */
62 /* */
63 /* DATE NAME DESCRIPTION */
64 /* */
65 /* 05-19-2020 Kenneth Maxwell Initial Version 6.0 */
66 /* 09-30-2020 Kenneth Maxwell Modified comment(s), */
67 /* resulting in version 6.1 */
68 /* */
69 /**************************************************************************/
70 #ifdef GX_UTF8_SUPPORT
_gx_utility_utf8_string_backward_character_length_get(GX_STRING * string,INT start_index,UINT * glyph_len)71 UINT _gx_utility_utf8_string_backward_character_length_get(GX_STRING *string, INT start_index, UINT *glyph_len)
72 {
73 UINT len = 0;
74
75 /* Get glyph lengh of the character in backward direction. */
76 while (start_index >= 0)
77 {
78 len++;
79
80 if (((string -> gx_string_ptr[start_index] & 0x80) == 0) ||
81 ((string -> gx_string_ptr[start_index] & 0xC0) == 0xC0))
82 {
83 /* End loop when byte match 0xxxxxxx or 11xxxxxx. */
84 break;
85 }
86
87 start_index--;
88 }
89
90 *glyph_len = len;
91
92 return GX_SUCCESS;
93 }
94 #endif /* GX_UTF8_SUPPORT */
95
96
