1 files changed, 54 insertions, 4 deletions

diff --git a/main.c b/main.c
index f9e9f41..b52e32d 100644
--- a/main.c
+++ b/main.c
@@ -56,7 +56,7 @@ typedef struct {
 LIST_AUTO(C4GroupEntryData, GroupEntryList)
 #define ForeachGroupEntry(list) LIST_FOREACH(GroupEntryList, list, entry)
 
-__off_t fileSizeFd(int fd)
+off_t fileSizeFd(int fd)
 {
 	struct stat st;
 
@@ -292,8 +292,52 @@ int main(int argc, char* argv[])
 	size_t uncompressedSize = last->Offset + last->Size;
 
 	currentSize += uncompressedSize;
-	header = realloc(header, currentSize);
-	uint8_t* data = (void*)(header) + sizeof(C4GroupHeader) + sizeof(C4GroupEntryCore) * header->Entries;
+
+#define TMP_FILE "cc4group.tmp"
+	int tmpFile = open(TMP_FILE, O_CREAT | O_RDWR | O_TRUNC | O_EXCL, 0600);
+	if(tmpFile == -1)
+	{
+		fprintf(stderr, "ERROR: Opening tmp file \"%s\": %s\n", "cc4group.tmp", strerror(errno));
+		return EXIT_FAILURE;
+	}
+
+	if(unlink(TMP_FILE) == -1)
+	{
+		fprintf(stderr, "ERROR: Deleting tmp file \"%s\". Manual deletion is required: %s\n", TMP_FILE, strerror(errno));
+	}
+#undef TMP_FILE
+
+	// allocate file size
+	// https://gist.github.com/marcetcheverry/991042
+	if(lseek(tmpFile, currentSize - 1, SEEK_SET) == -1)
+	{
+		fprintf(stderr, "ERROR: Seeking the tmp file to the end: %s\n", strerror(errno));
+		return EXIT_FAILURE;
+	}
+
+	if(write(tmpFile, "", 1) == -1)
+	{
+		fprintf(stderr, "ERROR: Writing to the tmp file's end: %s\n", strerror(errno));
+		return EXIT_FAILURE;
+	}
+
+	uint8_t* mmappedHeader = mmap(NULL, currentSize, PROT_READ | PROT_WRITE, MAP_SHARED, tmpFile, 0);
+	if(mmappedHeader == MAP_FAILED)
+	{
+		fprintf(stderr, "ERROR: Mapping tmp file: %s\n", strerror(errno));
+		return EXIT_FAILURE;
+	}
+
+	if(close(tmpFile) == -1)
+	{
+		fprintf(stderr, "ERROR: Closing tmp file \"cc4group.tmp\": %s\n", strerror(errno));
+		return EXIT_FAILURE;
+	}
+
+	uint8_t* data = (void*)(mmappedHeader) + sizeof(C4GroupHeader) + sizeof(C4GroupEntryCore) * header->Entries;
+
+	// write alredy decompressed header and cores into the file
+	memcpy(mmappedHeader, header, data - mmappedHeader);
 
 	strm.next_out = data;
 	strm.avail_out = uncompressedSize;
@@ -313,7 +357,7 @@ int main(int argc, char* argv[])
 		return EXIT_FAILURE;
 	}
 
-	C4GroupEntryData root = {.data = (uint8_t*)header, .children = NULL};
+	C4GroupEntryData root = {.data = (uint8_t*)mmappedHeader, .children = NULL};
 	buildChildren(&root);
 
 	handleChildren(root.children, 0, argv[2]);
@@ -322,5 +366,11 @@ int main(int argc, char* argv[])
 
 	free(header);
 
+	if(munmap(mmappedHeader, size) == -1)
+	{
+		fprintf(stderr, "ERROR: Unmapping tmp file: %s\n", strerror(errno));
+		return EXIT_FAILURE;
+	}
+
 	return EXIT_SUCCESS;
 }