GUACAMOLE-313: Use binary search to find human-readable names for known keys.

src/guaclog/key-name.c

@@ -22,12 +22,107 @@
 #include "log.h"
 
 #include <stdio.h>
+#include <stdlib.h>
+
+/**
+ * A mapping of X11 keysym to its corresponding human-readable name.
+ */
+typedef struct guaclog_known_key {
+
+    /**
+     * The X11 keysym of the key.
+     */
+    const int keysym;
+
+    /**
+     * A human-readable name for the key.
+     */
+    const char* name;
+
+} guaclog_known_key;
+
+/**
+ * All known keys.
+ */
+const guaclog_known_key known_keys[] = {
+    { 0xFFE1, "Shift" }
+};
+
+/**
+ * Comparator for the standard bsearch() function which compares an integer
+ * keysym against the keysym associated with a guaclog_known_key.
+ *
+ * @param key
+ *     The key value being compared against the member. This MUST be the
+ *     keysym value, passed through typecasting to an intptr_t (NOT a pointer
+ *     to the int itself).
+ *
+ * @param member
+ *     The member within the known_keys array being compared against the given
+ *     key.
+ *
+ * @return
+ *     Zero if the given keysym is equal to that of the given member, a
+ *     positive value if the given keysym is greater than that of the given
+ *     member, or a negative value if the given keysym is less than that of the
+ *     given member.
+ */
+static int guaclog_known_key_bsearch_compare(const void* key,
+        const void* member) {
+
+    int keysym = (int) ((intptr_t) key);
+    guaclog_known_key* current = (guaclog_known_key*) member;
+
+    /* Compare given keysym to keysym of current member */
+    return keysym  - current->keysym;
+
+}
+
+/**
+ * Searches through the known_keys array of known keys for the name of the key
+ * having the given keysym. If found, the name of the keysym is copied into the
+ * given buffer, which must be at least GUACLOG_MAX_KEY_NAME_LENGTH bytes long.
+ *
+ * @param key_name
+ *     The buffer to copy the key name into, which must be at least
+ *     GUACLOG_MAX_KEY_NAME_LENGTH.
+ *
+ * @param keysym
+ *     The X11 keysym of the key whose name should be stored in
+ *     key_name.
+ *
+ * @return
+ *     The length of the name, in bytes, excluding null terminator, or zero if
+ *     the key could not be found.
+ */
+static int guaclog_locate_key_name(char* key_name, int keysym) {
+
+    /* Search through known keys for given keysym */
+    guaclog_known_key* found = bsearch((void*) ((intptr_t) keysym),
+            known_keys, sizeof(known_keys) / sizeof(known_keys[0]),
+            sizeof(known_keys[0]), guaclog_known_key_bsearch_compare);
+
+    /* If found, format name and return length of result */
+    if (found != NULL)
+        return snprintf(key_name, GUACLOG_MAX_KEY_NAME_LENGTH,
+                "[ %s ]", found->name);
+
+    /* Key not found */
+    return 0;
+
+}
 
 int guaclog_key_name(char* key_name, int keysym) {
 
+    int name_length;
+
+    /* Search for name within list of known keys */
+    name_length = guaclog_locate_key_name(key_name, keysym);
+
     /* Fallback to using hex keysym as name */
-    int name_length = snprintf(key_name, GUACLOG_MAX_KEY_NAME_LENGTH,
-            "0x%X", keysym);
+    if (name_length == 0)
+        name_length = snprintf(key_name, GUACLOG_MAX_KEY_NAME_LENGTH,
+                "0x%X", keysym);
 
     /* Truncate name if necessary */
     if (name_length >= GUACLOG_MAX_KEY_NAME_LENGTH) {