Drag memory-mapped file handling into C++

memfile.cpp

@@ -0,0 +1,73 @@
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/mman.h>
+
+extern "C" {
+	#include "memfile.h"
+}
+
+#define INCREMENT 131072
+
+struct memfile *memfile_open(int fd) {
+	if (ftruncate(fd, INCREMENT) != 0) {
+		return NULL;
+	}
+
+	char *map = (char *) mmap(NULL, INCREMENT, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+	if (map == MAP_FAILED) {
+		return NULL;
+	}
+
+	struct memfile *mf = (struct memfile *) malloc(sizeof(struct memfile));
+	if (mf == NULL) {
+		munmap(map, INCREMENT);
+		return NULL;
+	}
+
+	mf->fd = fd;
+	mf->map = map;
+	mf->len = INCREMENT;
+	mf->off = 0;
+	mf->tree = 0;
+
+	return mf;
+}
+
+int memfile_close(struct memfile *file) {
+	if (munmap(file->map, file->len) != 0) {
+		return -1;
+	}
+
+	if (file->fd >= 0) {
+		if (close(file->fd) != 0) {
+			return -1;
+		}
+	}
+
+	free(file);
+	return 0;
+}
+
+int memfile_write(struct memfile *file, void *s, long long len) {
+	if (file->off + len > file->len) {
+		if (munmap(file->map, file->len) != 0) {
+			return -1;
+		}
+
+		file->len += INCREMENT;
+
+		if (ftruncate(file->fd, file->len) != 0) {
+			return -1;
+		}
+
+		file->map = (char *) mmap(NULL, file->len, PROT_READ | PROT_WRITE, MAP_SHARED, file->fd, 0);
+		if (file->map == MAP_FAILED) {
+			return -1;
+		}
+	}
+
+	memcpy(file->map + file->off, s, len);
+	file->off += len;
+	return len;
+}