From 3431e43f1e067f62bb3b94bebe302954c91e44a8 Mon Sep 17 00:00:00 2001
From: Natalia Portillo <claunia@claunia.com>
Date: Wed, 22 Sep 2021 00:01:36 +0100
Subject: [PATCH] Add Fletcher-32.

---
 CMakeLists.txt |  2 +-
 fletcher32.c   | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++
 fletcher32.h   | 34 ++++++++++++++++++++++++++
 3 files changed, 101 insertions(+), 1 deletion(-)
 create mode 100644 fletcher32.c
 create mode 100644 fletcher32.h

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8c48256..0a05e24 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -3,4 +3,4 @@ project("Aaru.Checksums.Native" C)
 
 set(CMAKE_C_STANDARD 90)
 
-add_library("Aaru.Checksums.Native" SHARED adler32.h adler32.c crc16.h crc16.c crc16_ccitt.h crc16_ccitt.c crc32.c crc32.h crc64.c crc64.h fletcher16.h fletcher16.c library.h)
+add_library("Aaru.Checksums.Native" SHARED adler32.h adler32.c crc16.h crc16.c crc16_ccitt.h crc16_ccitt.c crc32.c crc32.h crc64.c crc64.h fletcher16.h fletcher16.c fletcher32.h fletcher32.c library.h)
diff --git a/fletcher32.c b/fletcher32.c
new file mode 100644
index 0000000..27954a6
--- /dev/null
+++ b/fletcher32.c
@@ -0,0 +1,66 @@
+/*
+ * This file is part of the Aaru Data Preservation Suite.
+ * Copyright (c) 2019-2021 Natalia Portillo.
+ *
+ * This library is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation; either version 2.1 of the
+ * License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdint.h>
+#include <stdlib.h>
+
+#include "library.h"
+
+#include "fletcher32.h"
+
+AARU_EXPORT fletcher32_ctx* AARU_CALL fletcher32_init()
+{
+    fletcher32_ctx* ctx;
+
+    ctx = (fletcher32_ctx*)malloc(sizeof(fletcher32_ctx));
+
+    if(!ctx) return NULL;
+
+    ctx->sum1 = 0xFFFF;
+    ctx->sum2 = 0xFFFF;
+
+    return ctx;
+}
+
+AARU_EXPORT int AARU_CALL fletcher32_update(fletcher32_ctx* ctx, const uint8_t* data, uint32_t len)
+{
+    if(!ctx || !data) return -1;
+
+    for(uint32_t i = 0; i < len; i++)
+    {
+        ctx->sum1 = (ctx->sum1 + data[i]) % FLETCHER32_MODULE;
+        ctx->sum2 = (ctx->sum2 + ctx->sum1) % FLETCHER32_MODULE;
+    }
+
+    return 0;
+}
+
+AARU_EXPORT int AARU_CALL fletcher32_final(fletcher32_ctx* ctx, uint32_t* checksum)
+{
+    if(!ctx) return -1;
+
+    *checksum = (ctx->sum2 << 16) | ctx->sum1;
+    return 0;
+}
+
+AARU_EXPORT void AARU_CALL fletcher32_free(fletcher32_ctx* ctx)
+{
+    if(!ctx) return;
+
+    free(ctx);
+}
\ No newline at end of file
diff --git a/fletcher32.h b/fletcher32.h
new file mode 100644
index 0000000..8ace23f
--- /dev/null
+++ b/fletcher32.h
@@ -0,0 +1,34 @@
+/*
+ * This file is part of the Aaru Data Preservation Suite.
+ * Copyright (c) 2019-2021 Natalia Portillo.
+ *
+ * This library is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation; either version 2.1 of the
+ * License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef AARU_CHECKSUMS_NATIVE_FLETCHER32_H
+#define AARU_CHECKSUMS_NATIVE_FLETCHER32_H
+
+#define FLETCHER32_MODULE 0xFFFF
+
+typedef struct {
+    uint16_t sum1;
+    uint16_t sum2;
+} fletcher32_ctx;
+
+AARU_EXPORT fletcher32_ctx* AARU_CALL fletcher32_init();
+AARU_EXPORT int AARU_CALL fletcher32_update(fletcher32_ctx* ctx, const uint8_t* data, uint32_t len);
+AARU_EXPORT int AARU_CALL fletcher32_final(fletcher32_ctx* ctx, uint32_t* checksum);
+AARU_EXPORT void AARU_CALL fletcher32_free(fletcher32_ctx* ctx);
+
+#endif//AARU_CHECKSUMS_NATIVE_FLETCHER32_H