Add table walker to libx52util

This file walks the generated table to find the corresponding character
map values for the given UTF-8 string.

util/libx52util.h

@@ -0,0 +1,43 @@
+/*
+ * Saitek X52 Pro Utility Library
+ *
+ * Copyright (C) 2015 Nirenjan Krishnan (nirenjan@nirenjan.org)
+ *
+ *  This program is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU General Public License as
+ *  published by the Free Software Foundation, version 2.
+ *
+ */
+
+#ifndef LIBX52UTIL_H
+#define LIBX52UTIL_H
+
+#include <time.h>
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief Convert UTF8 string to X52 character map.
+ *
+ * This function takes in a UTF-8 string and converts it to the character
+ * map used by the X52Pro MFD. Unrecognized characters are silently dropped.
+ *
+ * @param[in]       input   Input string in UTF-8. Must be NUL-terminated
+ * @param[out]      output  Output buffer
+ * @param[inout]    len     Length of output buffer
+ *
+ * @returns 0 on success, -EINVAL on invalid parameters, -E2BIG if the buffer
+ * filled up before converting the entire string.
+ */
+int libx52util_convert_utf8_string(const uint8_t *input,
+                                   uint8_t *output, size_t *len);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* !defined LIBX52UTIL_H */
+

util/x52_char_map.h

@@ -29,4 +29,6 @@ struct map_entry {
     uint8_t value;          /* Value is valid if this is of TYPE_ENTRY */
 };
 
+extern struct map_entry map_root[];
+
 #endif /* !defined X52_CHAR_MAP_H */

util/x52_char_map_lookup.c

@@ -0,0 +1,86 @@
+/*
+ * Saitek X52 Pro Character Map Lookup
+ *
+ * This file implements functions to perform a lookup of a UTF-8 character
+ * in the generated lookup table.
+ *
+ * Copyright (C) 2015 Nirenjan Krishnan (nirenjan@nirenjan.org)
+ *
+ *  This program is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU General Public License as
+ *  published by the Free Software Foundation, version 2.
+ *
+ */
+
+#include <stdint.h>
+#include <errno.h>
+
+#include "libx52util.h"
+#include "x52_char_map.h"
+
+/**
+ * @brief Convert UTF8 string to X52 character map.
+ *
+ * This function takes in a UTF-8 string and converts it to the character
+ * map used by the X52Pro MFD. Unrecognized characters are silently dropped.
+ *
+ * @param[in]       input   Input string in UTF-8. Must be NUL-terminated
+ * @param[out]      output  Output buffer
+ * @param[inout]    len     Length of output buffer
+ *
+ * @returns 0 on success, -EINVAL on invalid parameters, -E2BIG if the buffer
+ * filled up before converting the entire string.
+ */
+int libx52util_convert_utf8_string(const uint8_t *input,
+                                   uint8_t *output, size_t *len)
+{
+    struct map_entry *entry;
+    size_t index;
+    int retval = 0;
+    unsigned char local_index;
+
+    if (!input || !output || !len || !*len) {
+        return -EINVAL;
+    }
+
+    index = 0;
+    entry = &map_root[*input];
+    while (*input) {
+        input++;
+        if (entry->type == TYPE_ENTRY) {
+            output[index] = entry->value;
+            index++;
+            if (index >= *len) {
+                retval = -E2BIG;
+                break;
+            }
+            entry = &map_root[*input];
+        } else if (entry->type == TYPE_POINTER) {
+            local_index = *input;
+            if (local_index < 0x80 || local_index >= 0xC0) {
+                /* Invalid input, skip till we find the start of another
+                 * valid UTF-8 character
+                 */
+                while (*input >= 0x80 && *input < 0xC0) {
+                    input++; /* Skip invalid characters */
+                }
+
+                /* New UTF-8 character, reset the entry pointer */
+                entry = &map_root[*input];
+            } else {
+                /* Mask off the upper bits, we only care about the lower 6 bits */
+                local_index &= 0x3F;
+                entry = &(entry->next[local_index]);
+            }
+        } else {
+            /* Invalid value, skip */
+            while (*input >= 0x80 && *input < 0xC0) {
+                input++; /* Skip invalid characters */
+            }
+        }
+    }
+
+    *len = index;
+    return retval;
+}
+