input: Map the mappings instead of reading them

This makes the operation take 0.5ms, compared to 1ms previously, and
allows the page to be shared with other GLFW programs running
concurrently.

src/cache.c

@@ -34,9 +34,11 @@
 #error "libxxhash is required for the compose cache"
 #endif
 
+#include <fcntl.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/mman.h>
 #include <sys/stat.h>
 #include <unistd.h>
 #define XXH_INLINE_ALL
@@ -126,53 +128,30 @@ cacheGetPathFromString(const char *string, char **cachePath)
 GLFWbool
 cacheRead(const char *path, _GLFWmapping** out, int* count)
 {
-    FILE *f;
-    int length, i;
-    _GLFWmapping* mappings;
-    _GLFWmapping* mapping;
+    int fd;
+    int length;
+    void* map;
 
-#define FREAD(ptr, size, nmemb, stream) \
-    do \
-    { \
-        if (fread(ptr, size, nmemb, stream) < nmemb) \
-            return GLFW_FALSE; \
-    } while (0)
-#define FREAD_n(ptr, nmemb, stream) \
-    FREAD(ptr, sizeof(*ptr), nmemb, stream)
-#define FREAD_1(value, stream) \
-    FREAD_n(&value, 1, stream)
-
-    f = fopen(path, "rb");
-    if (!f)
+    fd = open(path, O_RDONLY);
+    if (fd < 0)
         return GLFW_FALSE;
 
-    FREAD_1(length, f);
-    mappings = malloc(length * sizeof(_GLFWmapping));
-    if (!mappings)
-        goto error;
-
-    for (i = 0; i < length; ++i)
+    if (read(fd, &length, 4) != 4)
     {
-        mapping = &mappings[i];
-        FREAD_n(mapping->name, 128, f);
-        FREAD_n(mapping->guid, 16, f);
-        FREAD_n(mapping->buttons, 15, f);
-        FREAD_n(mapping->axes, 6, f);
+        close(fd);
+        return GLFW_FALSE;
     }
 
-#undef FREAD_1
-#undef FREAD_n
-#undef FREAD
+    map = mmap(NULL, 4 + length * sizeof(_GLFWmapping), PROT_READ, MAP_PRIVATE, fd, 0);
+    if (map == MAP_FAILED)
+    {
+        close(fd);
+        return GLFW_FALSE;
+    }
 
-    fclose(f);
     *count = length;
-    *out = mappings;
+    *out = map + 4;
     return GLFW_TRUE;
-
-error:
-    fclose(f);
-    unlink(path);
-    return GLFW_FALSE;
 }
 
 void

src/init.c

@@ -36,6 +36,10 @@
 #include <stdarg.h>
 #include <assert.h>
 
+#ifdef HAVE_XXHASH
+#include <sys/mman.h>
+#endif
+
 
 // The global variables below comprise all mutable global data in GLFW
 //
@@ -86,7 +90,12 @@ static void terminate(void)
     _glfw.monitors = NULL;
     _glfw.monitorCount = 0;
 
-    free(_glfw.mappings);
+#ifdef HAVE_XXHASH
+    if (_glfw.mappingMmapped)
+        munmap((void*)_glfw.mappings - 4, 4 + _glfw.mappingCount * sizeof(_GLFWmapping));
+    else
+#endif
+        free(_glfw.mappings);
     _glfw.mappings = NULL;
     _glfw.mappingCount = 0;
 

src/input.c

@@ -1194,7 +1194,7 @@ GLFWAPI int glfwUpdateGamepadMappings(const char* string)
     const char* c = string;
 #ifdef HAVE_XXHASH
     char *cachePath;
-    GLFWbool usableCache, readFromCache = GLFW_FALSE;
+    GLFWbool usableCache;
 #endif
 
     assert(string != NULL);
@@ -1206,9 +1206,10 @@ GLFWAPI int glfwUpdateGamepadMappings(const char* string)
 
     if (usableCache && cacheRead(cachePath, &_glfw.mappings, &_glfw.mappingCount))
     {
-        readFromCache = GLFW_TRUE;
+        _glfw.mappingMmapped = GLFW_TRUE;
         goto doMapping;
     }
+    _glfw.mappingMmapped = GLFW_FALSE;
 #endif
 
     while (*c)
@@ -1264,7 +1265,7 @@ doMapping:
     }
 
 #ifdef HAVE_XXHASH
-    if (usableCache && !readFromCache)
+    if (usableCache && !_glfw.mappingMmapped)
         cacheWrite(cachePath, _glfw.mappings, _glfw.mappingCount);
 
     free(cachePath);

src/internal.h

@@ -544,6 +544,9 @@ struct _GLFWlibrary
     _GLFWjoystick       joysticks[GLFW_JOYSTICK_LAST + 1];
     _GLFWmapping*       mappings;
     int                 mappingCount;
+#ifdef HAVE_XXHASH
+    GLFWbool            mappingMmapped;
+#endif
 
     _GLFWtls            errorSlot;
     _GLFWtls            contextSlot;