1 files changed, 109 insertions, 0 deletions
diff --git a/src/decompress.c b/src/decompress.c
new file mode 100644
index 0000000..dba637f
--- /dev/null
+++ b/src/decompress.c
@@ -0,0 +1,109 @@
+/* This file is part of Nekopack.
+
+   Copyright (C) 2017 Jakob Tsar-Fox, All Rights Reserved.
+
+   Nekopack is free software: you can redistribute it and/or modify it
+   under the terms of the GNU General Public License as published by the
+   Free Software Foundation, either version 3 of the License, or (at
+   your option) any later version.
+
+   Nekopack is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with Nekopack. If not, see <http://www.gnu.org/licenses/>. */
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <zlib.h>
+
+#include "defs.h"
+#include "extract.h"
+
+
+/* Document and put in header. */
+Bytef *inflate_chunk(Bytef *chunk, uint64_t chunk_size,
+                     uint64_t decompressed_size) {
+    Bytef *decompressed_data = malloc(decompressed_size);
+
+    if (decompressed_data == NULL) {
+        fprintf(stderr, "Insufficient memory to decompress archive.\n");
+        free(decompressed_data);
+        return NULL;
+    }
+
+    z_stream data_stream;
+    data_stream.zalloc = Z_NULL;
+    data_stream.zfree = Z_NULL;
+    data_stream.opaque = Z_NULL;
+    data_stream.avail_in = 0;
+    data_stream.next_in = Z_NULL;
+
+    if (inflateInit(&data_stream) != Z_OK) {
+        fprintf(stderr, "Could not initialize zlib.\n");
+        free(decompressed_data);
+        return NULL;
+    }
+
+    int status_code;
+    do {
+        data_stream.avail_in = chunk_size;
+        if (data_stream.avail_in == 0)
+            break;
+        data_stream.next_in = chunk;
+        // Flushing probably isn't required here.
+        do {
+            data_stream.avail_out = decompressed_size;
+            data_stream.next_out = decompressed_data;
+            status_code = inflate(&data_stream, Z_NO_FLUSH);
+        } while (data_stream.avail_out == 0);
+    } while (status_code != Z_STREAM_END);
+
+    inflateEnd(&data_stream);
+
+    return decompressed_data;
+}
+
+
+/* Wrapper for inflate_chunk which operates on FILE pointers. The file
+   pointer's contents are inflated into a memory stream and returned. */
+memory_stream decompress_file(FILE *archive, uint64_t sizes_offset) {
+    uint64_t compressed_size, decompressed_size;
+    fseek(archive, sizes_offset, SEEK_SET);
+    fread(&compressed_size, sizeof(uint64_t), 1, archive);
+    fread(&decompressed_size, sizeof(uint64_t), 1, archive);
+
+    /* Decompression is done in memory because it's $CURRENT_YEAR. */
+    Bytef *compressed_data = malloc(compressed_size);
+
+    /* This is a pretty shitty way of handling it, though. */
+    if (compressed_data == NULL) {
+        fprintf(stderr, "Insufficient memory to decompress archive.\n");
+        free(compressed_data);
+        fclose(archive);
+        exit(EXIT_FAILURE);
+    }
+
+    fread(compressed_data, compressed_size, 1, archive);
+    /* if (ferror(archive)) { */
+    /*     fprintf(stderr, "File corrupt.\n"); */
+    /*     inflateEnd(&data_stream); */
+    /*     free(compressed_data); */
+    /*     free(decompressed_data); */
+    /*     exit(EXIT_FAILURE); */
+    /* } */
+    Bytef *decompressed_data = inflate_chunk(compressed_data, compressed_size,
+                                             decompressed_size);
+
+    /* The compressed data is irrelevant at this point. */
+    free(compressed_data);
+    if (decompressed_data == NULL)
+        exit(EXIT_FAILURE);
+
+    return (memory_stream) {decompressed_size,
+                            decompressed_data,
+                            decompressed_data};
+}