Add some helper wrappers to mmap files

Alc/compat.h

@@ -25,6 +25,19 @@ FILE *al_fopen(const char *fname, const char *mode);
 
 #endif
 
+struct FileMapping {
+#ifdef _WIN32
+    HANDLE file;
+    HANDLE fmap;
+#else
+    int fd;
+#endif
+    void *ptr;
+    size_t len;
+};
+struct FileMapping MapFileToMem(const char *fname);
+void UnmapFileMem(const struct FileMapping *mapping);
+
 al_string GetProcPath(void);
 
 #ifdef HAVE_DYNLOAD

Alc/helpers.c

@@ -89,6 +89,10 @@ DEFINE_PROPERTYKEY(PKEY_AudioEndpoint_FormFactor, 0x1da5d803, 0xd492, 0x4edd, 0x
 #endif
 
 #ifndef _WIN32
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <fcntl.h>
 #include <unistd.h>
 #elif defined(_WIN32_IE)
 #include <shlobj.h>
@@ -598,6 +602,68 @@ vector_al_string SearchDataFiles(const char *ext, const char *subdir)
     return results;
 }
 
+
+struct FileMapping MapFileToMem(const char *fname)
+{
+    struct FileMapping ret = { NULL, NULL, NULL, 0 };
+    MEMORY_BASIC_INFORMATION meminfo;
+    HANDLE file, fmap;
+    WCHAR *wname;
+    void *ptr;
+
+    wname = FromUTF8(fname);
+
+    file = CreateFileW(wname, GENERIC_READ, FILE_SHARE_READ, NULL,
+                       OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
+    if(file == INVALID_HANDLE_VALUE)
+    {
+        ERR("Failed to open %s: %lu\n", fname, GetLastError());
+        free(wname);
+        return ret;
+    }
+    free(wname);
+    wname = NULL;
+
+    fmap = CreateFileMappingW(file, NULL, PAGE_READONLY, 0, 0, NULL);
+    if(!fmap)
+    {
+        ERR("Failed to create map for %s: %lu\n", fname, GetLastError());
+        CloseHandle(file);
+        return ret;
+    }
+
+    ptr = MapViewOfFile(fmap, FILE_MAP_READ, 0, 0, 0);
+    if(!ptr)
+    {
+        ERR("Failed to map %s: %lu\n", fname, GetLastError());
+        CloseHandle(fmap);
+        CloseHandle(file);
+        return ret;
+    }
+
+    if(VirtualQuery(ptr, &meminfo, sizeof(meminfo)) != sizeof(meminfo))
+    {
+        ERR("Failed to get map size for %s: %lu\n", fname, GetLastError());
+        UnmapViewOfFile(ptr);
+        CloseHandle(fmap);
+        CloseHandle(file);
+        return ret;
+    }
+
+    ret.file = file;
+    ret.fmap = fmap;
+    ret.ptr = ptr;
+    ret.len = meminfo.RegionSize;
+    return ret;
+}
+
+void UnmapFileMem(const struct FileMapping *mapping)
+{
+    UnmapViewOfFile(mapping->ptr);
+    CloseHandle(mapping->fmap);
+    CloseHandle(mapping->file);
+}
+
 #else
 
 al_string GetProcPath(void)
@@ -810,6 +876,47 @@ vector_al_string SearchDataFiles(const char *ext, const char *subdir)
     return results;
 }
 
+
+struct FileMapping MapFileToMem(const char *fname)
+{
+    struct FileMapping ret = { -1, NULL, 0 };
+    struct stat sbuf;
+    void *ptr;
+    int fd;
+
+    fd = open(fname, O_RDONLY, 0);
+    if(fd == -1)
+    {
+        ERR("Failed to open %s: (%d) %s\n", fname, errno, strerror(errno));
+        return ret;
+    }
+    if(fstat(fd, &sbuf) == -1)
+    {
+        ERR("Failed to stat %s: (%d) %s\n", fname, errno, strerror(errno));
+        close(fd);
+        return ret;
+    }
+
+    ptr = mmap(NULL, sbuf.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
+    if(ptr == MAP_FAILED)
+    {
+        ERR("Failed to map %s: (%d) %s\n", fname, errno, strerror(errno));
+        close(fd);
+        return ret;
+    }
+
+    ret.fd = fd;
+    ret.ptr = ptr;
+    ret.len = sbuf.st_size;
+    return ret;
+}
+
+void UnmapFileMem(const struct FileMapping *mapping)
+{
+    munmap(mapping->ptr, mapping->len);
+    close(mapping->fd);
+}
+
 #endif