From 026161027dda2add2a5082d3de230069501b5b82 Mon Sep 17 00:00:00 2001
From: Patrick McDermott <patrick.mcdermott@libiquity.com>
Date: Wed, 12 Apr 2023 22:55:14 -0400
Subject: gzip: Implement

---
(limited to 'src/gzip.c')

diff --git a/src/gzip.c b/src/gzip.c
new file mode 100644
index 0000000..328f33a
--- /dev/null
+++ b/src/gzip.c
@@ -0,0 +1,134 @@
+/*
+ * Copyright (C) 2023  Patrick McDermott
+ *
+ * This file is part of opkg-opkg.
+ *
+ * opkg-opkg 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.
+ *
+ * opkg-opkg 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 opkg-opkg.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdio.h>
+#include <zlib.h>
+#include "gzip.h"
+
+#define OPKG_OPK_GZIP_BUFFER_SIZE 8192
+
+struct opkg_opk_gzip_state {
+	FILE          *input_file;
+	unsigned char  input_buffer[OPKG_OPK_GZIP_BUFFER_SIZE];
+	z_stream       stream;
+};
+
+static int
+_opkg_opk_gzip_init(struct opkg_opk_gzip_state *state)
+{
+	state->stream.zalloc = Z_NULL;
+	state->stream.zfree  = Z_NULL;
+	state->stream.opaque = Z_NULL;
+	if (inflateInit(&state->stream) != Z_OK) {
+		return OPKG_OPK_GZIP_ERROR;
+	}
+	return OPKG_OPK_GZIP_OK;
+}
+
+int
+opkg_opk_gzip_init_from_file(struct opkg_opk_gzip_state *state,
+		const char *file_name)
+{
+	state->input_file = fopen(file_name, "rb");
+	if (state->input_file == NULL) {
+		return OPKG_OPK_GZIP_ERROR;
+	}
+	state->stream.next_in  = Z_NULL;
+	state->stream.avail_in = 0;
+	if (_opkg_opk_gzip_init(state) < OPKG_OPK_GZIP_OK) {
+		fclose(state->input_file);
+		return OPKG_OPK_GZIP_ERROR;
+	}
+	return OPKG_OPK_GZIP_OK;
+}
+
+int
+opkg_opk_gzip_init_from_memory(struct opkg_opk_gzip_state *state,
+		unsigned char *input, size_t input_size)
+{
+	state->input_file = NULL;
+	state->stream.next_in  = input;
+	state->stream.avail_in = input_size;
+	return _opkg_opk_gzip_init(state);
+}
+
+static int
+_opkg_opk_gzip_next_record_from_file(struct opkg_opk_gzip_state *state)
+{
+	for (;;) {
+		if (feof(state->input_file)) {
+			fclose(state->input_file);
+			state->input_file = NULL;
+			inflateEnd(&state->stream);
+			return OPKG_OPK_GZIP_OK;
+		}
+		if (state->stream.avail_in == 0) {
+			state->stream.avail_in = fread(state->input_buffer,
+					1, OPKG_OPK_GZIP_BUFFER_SIZE,
+					state->input_file);
+			if (ferror(state->input_file)) {
+				fclose(state->input_file);
+				state->input_file = NULL;
+				inflateEnd(&state->stream);
+				return OPKG_OPK_GZIP_ERROR;
+			}
+			state->stream.next_in = state->input_buffer;
+		}
+		if (state->stream.avail_out == 0) {
+			return OPKG_OPK_GZIP_OK;
+		}
+		switch (inflate(&state->stream, Z_SYNC_FLUSH)) {
+			case Z_OK:
+			case Z_STREAM_END:
+			case Z_BUF_ERROR:
+				break;
+			default:
+				fclose(state->input_file);
+				state->input_file = NULL;
+				inflateEnd(&state->stream);
+				return OPKG_OPK_GZIP_ERROR;
+		}
+	}
+}
+
+static int
+_opkg_opk_gzip_next_record_from_memory(struct opkg_opk_gzip_state *state)
+{
+	switch (inflate(&state->stream, Z_SYNC_FLUSH)) {
+		case Z_OK:
+			return OPKG_OPK_GZIP_OK;
+		case Z_STREAM_END:
+			return OPKG_OPK_GZIP_END;
+		default:
+			inflateEnd(&state->stream);
+			return OPKG_OPK_GZIP_ERROR;
+	}
+}
+
+int
+opkg_opk_gzip_next_record(struct opkg_opk_gzip_state *state, void *record)
+{
+	state->stream.next_out  = record;
+	state->stream.avail_out = 512;
+	if (state->input_file != NULL) {
+		return _opkg_opk_gzip_next_record_from_file(state);
+	} else {
+		return _opkg_opk_gzip_next_record_from_memory(state);
+	}
+}
--
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