// Copyright (C) 2004-2021 Artifex Software, Inc.
//
// This file is part of MuPDF.
//
// MuPDF is free software: you can redistribute it and/or modify it under the
// terms of the GNU Affero General Public License as published by the Free
// Software Foundation, either version 3 of the License, or (at your option)
// any later version.
//
// MuPDF 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 Affero General Public License for more
// details.
//
// You should have received a copy of the GNU Affero General Public License
// along with MuPDF. If not, see <https://www.gnu.org/licenses/agpl-3.0.en.html>
//
// Alternative licensing terms are available from the licensor.
// For commercial licensing, see <https://www.artifex.com/> or contact
// Artifex Software, Inc., 39 Mesa Street, Suite 108A, San Francisco,
// CA 94129, USA, for further information.

#include "mupdf/fitz.h"

#include <string.h>

#define MIN_BOMB (100 << 20)

size_t
fz_read(fz_context *ctx, fz_stream *stm, unsigned char *buf, size_t len)
{
	size_t count, n;

	count = 0;
	do
	{
		n = fz_available(ctx, stm, len);
		if (n > len)
			n = len;
		if (n == 0)
			break;

		memcpy(buf, stm->rp, n);
		stm->rp += n;
		buf += n;
		count += n;
		len -= n;
	}
	while (len > 0);

	return count;
}

static unsigned char skip_buf[4096];

size_t fz_skip(fz_context *ctx, fz_stream *stm, size_t len)
{
	size_t count, l, total = 0;

	while (len)
	{
		l = len;
		if (l > sizeof(skip_buf))
			l = sizeof(skip_buf);
		count = fz_read(ctx, stm, skip_buf, l);
		total += count;
		if (count < l)
			break;
		len -= count;
	}
	return total;
}

fz_buffer *
fz_read_all(fz_context *ctx, fz_stream *stm, size_t initial)
{
	return fz_read_best(ctx, stm, initial, NULL, 0);
}

fz_buffer *
fz_read_best(fz_context *ctx, fz_stream *stm, size_t initial, int *truncated, size_t worst_case)
{
	fz_buffer *buf = NULL;
	int check_bomb = (initial > 0);
	size_t n;

	fz_var(buf);

	if (truncated)
		*truncated = 0;

	if (worst_case == 0)
		worst_case = initial * 200;
	if (worst_case < MIN_BOMB)
		worst_case = MIN_BOMB;

	fz_try(ctx)
	{
		if (initial < 1024)
			initial = 1024;

		buf = fz_new_buffer(ctx, initial+1);

		while (1)
		{
			if (buf->len == buf->cap)
				fz_grow_buffer(ctx, buf);

			if (check_bomb && buf->len > worst_case)
				fz_throw(ctx, FZ_ERROR_FORMAT, "compression bomb detected");

			n = fz_read(ctx, stm, buf->data + buf->len, buf->cap - buf->len);
			if (n == 0)
				break;

			buf->len += n;
		}
	}
	fz_catch(ctx)
	{
		if (fz_caught(ctx) == FZ_ERROR_TRYLATER || fz_caught(ctx) == FZ_ERROR_SYSTEM)
		{
			fz_drop_buffer(ctx, buf);
			fz_rethrow(ctx);
		}
		if (truncated)
		{
			*truncated = 1;
			fz_report_error(ctx);
		}
		else
		{
			fz_drop_buffer(ctx, buf);
			fz_rethrow(ctx);
		}
	}

	return buf;
}

char *
fz_read_line(fz_context *ctx, fz_stream *stm, char *mem, size_t n)
{
	char *s = mem;
	int c = EOF;
	while (n > 1)
	{
		c = fz_read_byte(ctx, stm);
		if (c == EOF)
			break;
		if (c == '\r') {
			c = fz_peek_byte(ctx, stm);
			if (c == '\n')
				fz_read_byte(ctx, stm);
			break;
		}
		if (c == '\n')
			break;
		*s++ = c;
		n--;
	}
	if (n)
		*s = '\0';
	return (s == mem && c == EOF) ? NULL : mem;
}

int64_t
fz_tell(fz_context *ctx, fz_stream *stm)
{
	return stm->pos - (stm->wp - stm->rp);
}

void
fz_seek(fz_context *ctx, fz_stream *stm, int64_t offset, int whence)
{
	stm->avail = 0; /* Reset bit reading */
	if (stm->seek)
	{
		if (whence == 1)
		{
			offset += fz_tell(ctx, stm);
			whence = 0;
		}
		stm->seek(ctx, stm, offset, whence);
		stm->eof = 0;
	}
	else if (whence != 2)
	{
		if (whence == 0)
			offset -= fz_tell(ctx, stm);
		if (offset < 0)
			fz_warn(ctx, "cannot seek backwards");
		/* dog slow, but rare enough */
		while (offset-- > 0)
		{
			if (fz_read_byte(ctx, stm) == EOF)
			{
				fz_warn(ctx, "seek failed");
				break;
			}
		}
	}
	else
		fz_warn(ctx, "cannot seek");
}

fz_buffer *
fz_read_file(fz_context *ctx, const char *filename)
{
	fz_stream *stm;
	fz_buffer *buf = NULL;

	fz_var(buf);

	stm = fz_open_file(ctx, filename);
	fz_try(ctx)
	{
		buf = fz_read_all(ctx, stm, 0);
	}
	fz_always(ctx)
	{
		fz_drop_stream(ctx, stm);
	}
	fz_catch(ctx)
	{
		fz_rethrow(ctx);
	}

	return buf;
}

fz_buffer *
fz_try_read_file(fz_context *ctx, const char *filename)
{
	fz_stream *stm;
	fz_buffer *buf = NULL;

	fz_var(buf);

	stm = fz_try_open_file(ctx, filename);
	if (stm == NULL)
		return NULL;
	fz_try(ctx)
	{
		buf = fz_read_all(ctx, stm, 0);
	}
	fz_always(ctx)
	{
		fz_drop_stream(ctx, stm);
	}
	fz_catch(ctx)
	{
		fz_rethrow(ctx);
	}

	return buf;
}

uint16_t fz_read_uint16(fz_context *ctx, fz_stream *stm)
{
	int a = fz_read_byte(ctx, stm);
	int b = fz_read_byte(ctx, stm);
	if (a == EOF || b == EOF)
		fz_throw(ctx, FZ_ERROR_FORMAT, "premature end of file in int16");
	return ((uint16_t)a<<8) | ((uint16_t)b);
}

uint32_t fz_read_uint24(fz_context *ctx, fz_stream *stm)
{
	int a = fz_read_byte(ctx, stm);
	int b = fz_read_byte(ctx, stm);
	int c = fz_read_byte(ctx, stm);
	if (a == EOF || b == EOF || c == EOF)
		fz_throw(ctx, FZ_ERROR_FORMAT, "premature end of file in int24");
	return ((uint32_t)a<<16) | ((uint32_t)b<<8) | ((uint32_t)c);
}

uint32_t fz_read_uint32(fz_context *ctx, fz_stream *stm)
{
	int a = fz_read_byte(ctx, stm);
	int b = fz_read_byte(ctx, stm);
	int c = fz_read_byte(ctx, stm);
	int d = fz_read_byte(ctx, stm);
	if (a == EOF || b == EOF || c == EOF || d == EOF)
		fz_throw(ctx, FZ_ERROR_FORMAT, "premature end of file in int32");
	return ((uint32_t)a<<24) | ((uint32_t)b<<16) | ((uint32_t)c<<8) | ((uint32_t)d);
}

uint64_t fz_read_uint64(fz_context *ctx, fz_stream *stm)
{
	int a = fz_read_byte(ctx, stm);
	int b = fz_read_byte(ctx, stm);
	int c = fz_read_byte(ctx, stm);
	int d = fz_read_byte(ctx, stm);
	int e = fz_read_byte(ctx, stm);
	int f = fz_read_byte(ctx, stm);
	int g = fz_read_byte(ctx, stm);
	int h = fz_read_byte(ctx, stm);
	if (a == EOF || b == EOF || c == EOF || d == EOF || e == EOF || f == EOF || g == EOF || h == EOF)
		fz_throw(ctx, FZ_ERROR_FORMAT, "premature end of file in int64");
	return ((uint64_t)a<<56) | ((uint64_t)b<<48) | ((uint64_t)c<<40) | ((uint64_t)d<<32)
		| ((uint64_t)e<<24) | ((uint64_t)f<<16) | ((uint64_t)g<<8) | ((uint64_t)h);
}

uint16_t fz_read_uint16_le(fz_context *ctx, fz_stream *stm)
{
	int a = fz_read_byte(ctx, stm);
	int b = fz_read_byte(ctx, stm);
	if (a == EOF || b == EOF)
		fz_throw(ctx, FZ_ERROR_FORMAT, "premature end of file in int16");
	return ((uint16_t)a) | ((uint16_t)b<<8);
}

uint32_t fz_read_uint24_le(fz_context *ctx, fz_stream *stm)
{
	int a = fz_read_byte(ctx, stm);
	int b = fz_read_byte(ctx, stm);
	int c = fz_read_byte(ctx, stm);
	if (a == EOF || b == EOF || c == EOF)
		fz_throw(ctx, FZ_ERROR_FORMAT, "premature end of file in int24");
	return ((uint32_t)a) | ((uint32_t)b<<8) | ((uint32_t)c<<16);
}

uint32_t fz_read_uint32_le(fz_context *ctx, fz_stream *stm)
{
	int a = fz_read_byte(ctx, stm);
	int b = fz_read_byte(ctx, stm);
	int c = fz_read_byte(ctx, stm);
	int d = fz_read_byte(ctx, stm);
	if (a == EOF || b == EOF || c == EOF || d == EOF)
		fz_throw(ctx, FZ_ERROR_FORMAT, "premature end of file in int32");
	return ((uint32_t)a) | ((uint32_t)b<<8) | ((uint32_t)c<<16) | ((uint32_t)d<<24);
}

uint64_t fz_read_uint64_le(fz_context *ctx, fz_stream *stm)
{
	int a = fz_read_byte(ctx, stm);
	int b = fz_read_byte(ctx, stm);
	int c = fz_read_byte(ctx, stm);
	int d = fz_read_byte(ctx, stm);
	int e = fz_read_byte(ctx, stm);
	int f = fz_read_byte(ctx, stm);
	int g = fz_read_byte(ctx, stm);
	int h = fz_read_byte(ctx, stm);
	if (a == EOF || b == EOF || c == EOF || d == EOF || e == EOF || f == EOF || g == EOF || h == EOF)
		fz_throw(ctx, FZ_ERROR_FORMAT, "premature end of file in int64");
	return ((uint64_t)a) | ((uint64_t)b<<8) | ((uint64_t)c<<16) | ((uint64_t)d<<24)
		| ((uint64_t)e<<32) | ((uint64_t)f<<40) | ((uint64_t)g<<48) | ((uint64_t)h<<56);
}

int16_t fz_read_int16(fz_context *ctx, fz_stream *stm) { return (int16_t)fz_read_uint16(ctx, stm); }
int32_t fz_read_int32(fz_context *ctx, fz_stream *stm) { return (int32_t)fz_read_uint32(ctx, stm); }
int64_t fz_read_int64(fz_context *ctx, fz_stream *stm) { return (int64_t)fz_read_uint64(ctx, stm); }

int16_t fz_read_int16_le(fz_context *ctx, fz_stream *stm) { return (int16_t)fz_read_uint16_le(ctx, stm); }
int32_t fz_read_int32_le(fz_context *ctx, fz_stream *stm) { return (int32_t)fz_read_uint32_le(ctx, stm); }
int64_t fz_read_int64_le(fz_context *ctx, fz_stream *stm) { return (int64_t)fz_read_uint64_le(ctx, stm); }

float
fz_read_float_le(fz_context *ctx, fz_stream *stm)
{
	union {float f;int32_t i;} u;

	u.i = fz_read_int32_le(ctx, stm);
	return u.f;
}

float
fz_read_float(fz_context *ctx, fz_stream *stm)
{
	union {float f;int32_t i;} u;

	u.i = fz_read_int32(ctx, stm);
	return u.f;
}

void fz_read_string(fz_context *ctx, fz_stream *stm, char *buffer, int len)
{
	int c;
	do
	{
		if (len <= 0)
			fz_throw(ctx, FZ_ERROR_FORMAT, "Buffer overrun reading null terminated string");

		c = fz_read_byte(ctx, stm);
		if (c == EOF)
			fz_throw(ctx, FZ_ERROR_FORMAT, "EOF reading null terminated string");
		*buffer++ = c;
		len--;
	}
	while (c != 0);
}

int fz_read_rune(fz_context *ctx, fz_stream *in)
{
	uint8_t d, e, f;
	int x;
	int c = fz_read_byte(ctx, in);
	if (c == EOF)
		return EOF;

	if ((c & 0xF8) == 0xF0)
	{
		x = fz_read_byte(ctx, in);
		if (x == EOF)
			return 0xFFFD;
		d = (uint8_t)x;
		c = (c & 7)<<18;
		if ((d & 0xC0) == 0x80)
		{
			x = fz_read_byte(ctx, in);
			if (x == EOF)
				return 0xFFFD;
			e = (uint8_t)x;
			c += (d & 0x3f)<<12;
			if ((e & 0xC0) == 0x80)
			{
				x = fz_read_byte(ctx, in);
				if (x == EOF)
					return 0xFFFD;
				f = (uint8_t)x;
				c += (e & 0x3f)<<6;
				if ((f & 0xC0) == 0x80)
				{
					c += f & 0x3f;
				}
				else
					goto bad_byte;
			}
			else
				goto bad_byte;
		}
		else
			goto bad_byte;
	}
	else if ((c & 0xF0) == 0xE0)
	{
		x = fz_read_byte(ctx, in);
		if (x == EOF)
			return 0xFFFD;
		d = (uint8_t)x;
		c = (c & 15)<<12;
		if ((d & 0xC0) == 0x80)
		{
			x = fz_read_byte(ctx, in);
			if (x == EOF)
				return 0xFFFD;
			e = (uint8_t)x;
			c += (d & 0x3f)<<6;
			if ((e & 0xC0) == 0x80)
			{
				c += e & 0x3f;
			}
			else
				goto bad_byte;
		}
		else
			goto bad_byte;
	}
	else if ((c & 0xE0) == 0xC0)
	{
		x = fz_read_byte(ctx, in);
		if (x == EOF)
			return 0xFFFD;
		d = (uint8_t)x;
		c = (c & 31)<<6;
		if ((d & 0xC0) == 0x80)
		{
			c += d & 0x3f;
		}
		else
			fz_unread_byte(ctx, in);
	}
	else if ((c & 0xc0) == 0x80)
	{
bad_byte:
		fz_unread_byte(ctx, in);
		return 0xFFFD;
	}

	return c;

}

int fz_read_utf16_le(fz_context *ctx, fz_stream *stm)
{
	int c = fz_read_byte(ctx, stm);
	int d, e;

	if (c == EOF)
		return EOF;

	d = fz_read_byte(ctx, stm);
	if (d == EOF)
		return c; /* Might be wrong, but the best we can do. */

	c |= d<<8;

	/* If it's not a surrogate, we're done. */
	if (c < 0xd800 || c >= 0xe000)
		return c;

	/* It *ought* to be a leading (high) surrogate. If it's not,
	 * then we're in trouble. */
	if (c >= 0xdc00)
		return 0x10000 + c - 0xdc00; /* Imagine the high surrogate was 0. */

	/* Our stream abstraction only enables us to peek 1 byte ahead, and we'd need
	 * 2 to tell if it was a low surrogate. Just assume it is. */
	d = fz_read_byte(ctx, stm);
	if (d == EOF)
	{
		/* Failure! Imagine the trailing surrogate was 0. */
		return 0x10000 + ((c - 0xd800)<<10);
	}
	e = fz_read_byte(ctx, stm);
	if (e == EOF)
	{
		e = 0xDC; /* Fudge a low surrogate */
	}

	d |= e<<8;

	if (d < 0xdc00 || d >= 0xe000)
	{
		/* Bad encoding! This is nasty, because we've eaten 2 bytes from the
		 * stream which ideally we would not have. Serves you right for
		 * having a broken stream. */
		return 0x10000 + ((c - 0xd800)<<10); /* Imagine the high surrogate was 0. */
	}

	c -= 0xd800;
	d -= 0xdc00;

	return 0x10000 + (c<<10) + d;
}

int fz_read_utf16_be(fz_context *ctx, fz_stream *stm)
{
	int c = fz_read_byte(ctx, stm);
	int d, e;

	if (c == EOF)
		return EOF;

	d = fz_read_byte(ctx, stm);
	if (d == EOF)
		return c; /* Might be wrong, but the best we can do. */

	c = (c<<8) | d;

	/* If it's not a surrogate, we're done. */
	if (c < 0xd800 || c >= 0xe000)
		return c;

	/* It *ought* to be a leading (high) surrogate. If it's not,
	 * then we're in trouble. */
	if (c >= 0xdc00)
		return 0x10000 + c - 0xdc00; /* Imagine the high surrogate was 0. */

	/* Our stream abstraction only enables us to peek 1 byte ahead, and we'd need
	 * 2 to tell if it was a low surrogate. Just assume it is. */
	d = fz_read_byte(ctx, stm);
	if (d == EOF)
	{
		/* Failure! Imagine the trailing surrogate was 0. */
		return 0x10000 + ((c - 0xd800)<<10);
	}

	/* The next byte ought to be the start of a trailing (low) surrogate. */
	if (d < 0xdc || d >= 0xe0)
	{
		/* It wasn't. Put the byte back. */
		fz_unread_byte(ctx, stm);
		d = 0xdc00; /* Pretend it was a 0 surrogate. */
	}
	else
	{
		e = fz_read_byte(ctx, stm);
		if (e == EOF)
		{
			e = 0;
		}
		d = (d<<8) | e;
	}

	c -= 0xd800;
	d -= 0xdc00;

	return 0x10000 + (c<<10) + d;
}