/*
 * Copyright 2015 Google Inc.
 *
 * SPDX-License-Identifier: GPL 2.0+ BSD-3-Clause
 */

#include <common.h>
#include <compiler.h>
#include <linux/kernel.h>
#include <linux/types.h>

static u16 LZ4_readLE16(const void *src) { return le16_to_cpu(*(u16 *)src); }
static void LZ4_copy4(void *dst, const void *src) { *(u32 *)dst = *(u32 *)src; }
static void LZ4_copy8(void *dst, const void *src) { *(u64 *)dst = *(u64 *)src; }

typedef  uint8_t BYTE;
typedef uint16_t U16;
typedef uint32_t U32;
typedef  int32_t S32;
typedef uint64_t U64;

#define FORCE_INLINE static inline __attribute__((always_inline))

/* Unaltered (except removing unrelated code) from github.com/Cyan4973/lz4. */
#include "lz4.c"	/* #include for inlining, do not link! */

#define LZ4F_MAGIC 0x184D2204

struct lz4_frame_header {
	u32 magic;
	union {
		u8 flags;
		struct {
			u8 reserved0:2;
			u8 has_content_checksum:1;
			u8 has_content_size:1;
			u8 has_block_checksum:1;
			u8 independent_blocks:1;
			u8 version:2;
		};
	};
	union {
		u8 block_descriptor;
		struct {
			u8 reserved1:4;
			u8 max_block_size:3;
			u8 reserved2:1;
		};
	};
	/* + u64 content_size iff has_content_size is set */
	/* + u8 header_checksum */
} __packed;

struct lz4_block_header {
	union {
		u32 raw;
		struct {
			u32 size:31;
			u32 not_compressed:1;
		};
	};
	/* + size bytes of data */
	/* + u32 block_checksum iff has_block_checksum is set */
} __packed;

int ulz4fn(const void *src, size_t srcn, void *dst, size_t *dstn)
{
	const void *end = dst + *dstn;
	const void *in = src;
	void *out = dst;
	int has_block_checksum;
	int ret;
	*dstn = 0;

	{ /* With in-place decompression the header may become invalid later. */
		const struct lz4_frame_header *h = in;

		if (srcn < sizeof(*h) + sizeof(u64) + sizeof(u8))
			return -EINVAL;	/* input overrun */

		/* We assume there's always only a single, standard frame. */
		if (le32_to_cpu(h->magic) != LZ4F_MAGIC || h->version != 1)
			return -EPROTONOSUPPORT;	/* unknown format */
		if (h->reserved0 || h->reserved1 || h->reserved2)
			return -EINVAL;	/* reserved must be zero */
		if (!h->independent_blocks)
			return -EPROTONOSUPPORT; /* we can't support this yet */
		has_block_checksum = h->has_block_checksum;

		in += sizeof(*h);
		if (h->has_content_size)
			in += sizeof(u64);
		in += sizeof(u8);
	}

	while (1) {
		struct lz4_block_header b = { .raw = le32_to_cpu(*(u32 *)in) };
		in += sizeof(struct lz4_block_header);

		if (in - src + b.size > srcn) {
			ret = -EINVAL;		/* input overrun */
			break;
		}

		if (!b.size) {
			ret = 0;	/* decompression successful */
			break;
		}

		if (b.not_compressed) {
			size_t size = min((ptrdiff_t)b.size, end - out);
			memcpy(out, in, size);
			out += size;
			if (size < b.size) {
				ret = -ENOBUFS;	/* output overrun */
				break;
			}
		} else {
			/* constant folding essential, do not touch params! */
			ret = LZ4_decompress_generic(in, out, b.size,
					end - out, endOnInputSize,
					full, 0, noDict, out, NULL, 0);
			if (ret < 0) {
				ret = -EPROTO;	/* decompression error */
				break;
			}
			out += ret;
		}

		in += b.size;
		if (has_block_checksum)
			in += sizeof(u32);
	}

	*dstn = out - dst;
	return ret;
}