/* -*- tab-width: 4; -*- */
/* vi: set sw=2 ts=4 expandtab: */

/*
 * ©2010-2018 The khronos Group, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @file
 * @~English
 *
 * @brief Implementation of ktxStream for FILE.
 *
 * @author Maksim Kolesin, Under Development
 * @author Georg Kolling, Imagination Technology
 * @author Mark Callow, HI Corporation
 */

#include <assert.h>
#include <errno.h>
#include <string.h>
/* I need these on Linux. Why? */
#define __USE_LARGEFILE 1  // For declaration of ftello, etc.
#define __USE_POSIX 1      // For declaration of fileno.
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>

#include "ktx.h"
#include "ktxint.h"
#include "filestream.h"

#if defined(_MSC_VER)
  #if defined(_WIN64)
    #define ftello _ftelli64
    #define fseeko _fseeki64
  #else
    #define ftello ftell
    #define fseeko fseek
  #endif
  #define fileno _fileno
#endif

#define KTX_FILE_STREAM_MAX (1 << (sizeof(ktx_off_t) - 1) - 1)

/**
 * @internal
 * @~English
 * @brief Read bytes from a ktxFileStream.
 *
 * @param [in]  str     pointer to the ktxStream from which to read.
 * @param [out] dst     pointer to a block of memory with a size
 *                      of at least @p size bytes, converted to a void*.
 * @param [in,out] count   pointer to total count of bytes to be read.
 *                         On completion set to number of bytes read.
 *
 * @return      KTX_SUCCESS on success, other KTX_* enum values on error.
 *
 * @exception KTX_INVALID_VALUE @p dst is @c NULL or @p src is @c NULL.
 * @exception KTX_FILE_UNEXPECTED_EOF not enough data to satisfy the request.
 */
static
KTX_error_code ktxFileStream_read(ktxStream* str, void* dst, const ktx_size_t count)
{
    ktx_size_t nread;

    if (!str || !dst)
        return KTX_INVALID_VALUE;

    assert(str->type == eStreamTypeFile);
    
    if ((nread = fread(dst, 1, count, str->data.file)) != count) {
        if (feof(str->data.file)) {
            return KTX_FILE_UNEXPECTED_EOF;
        } else
            return KTX_FILE_READ_ERROR;
    }

    return KTX_SUCCESS;
}

/**
 * @internal
 * @~English
 * @brief Skip bytes in a ktxFileStream.
 *
 * @param [in] str           pointer to a ktxStream object.
 * @param [in] count         number of bytes to be skipped.
 *
 * @return      KTX_SUCCESS on success, other KTX_* enum values on error.
 *
 * @exception KTX_INVALID_VALUE @p str is @c NULL or @p count is less than zero.
 * @exception KTX_INVALID_OPERATION skipping @p count bytes would go beyond EOF.
 * @exception KTX_FILE_UNEXPECTED_EOF not enough data to satisfy the request.
 *                                    @p count is set to the number of bytes
 *                                    skipped.
 */
static
KTX_error_code ktxFileStream_skip(ktxStream* str, const ktx_size_t count)
{
    ktx_size_t fileSize;
    ktx_off_t pos, newpos;

    if (!str)
        return KTX_INVALID_VALUE;

    assert(str->type == eStreamTypeFile);
    
    str->getsize(str, &fileSize);
    str->getpos(str, &pos);

    newpos = pos + count;
    /* First clause checks for overflow. */
    if (newpos < pos || pos + count > fileSize)
        return KTX_FILE_UNEXPECTED_EOF;

    if (fseeko(str->data.file, count, SEEK_CUR) != 0)
        return KTX_FILE_SEEK_ERROR;

    return KTX_SUCCESS;
}

/**
 * @internal
 * @~English
 * @brief Write bytes to a ktxFileStream.
 *
 * @param [in] str      pointer to the ktxStream that is the destination of the
 *                      write.
 * @param [in] src      pointer to the array of elements to be written,
 *                      converted to a const void*.
 * @param [in] size     size in bytes of each element to be written.
 * @param [in] count    number of elements, each one with a @p size of size
 *                      bytes.
 *
 * @return      KTX_SUCCESS on success, other KTX_* enum values on error.
 *
 * @exception KTX_INVALID_VALUE @p str is @c NULL or @p src is @c NULL.
 * @exception KTX_FILE_OVERFLOW the requested write would caused the file to
 *                              exceed the maximum supported file size.
 * @exception KTX_FILE_WRITE_ERROR a system error occurred while writing the
 *                                 file.
 */
static
KTX_error_code ktxFileStream_write(ktxStream* str, const void *src,
                                   const ktx_size_t size,
                                   const ktx_size_t count)
{
    if (!str || !src)
        return KTX_INVALID_VALUE;

    assert(str->type == eStreamTypeFile);
    
    if (fwrite(src, size, count, str->data.file) != count) {
        if (errno == EFBIG || errno == EOVERFLOW)
            return KTX_FILE_OVERFLOW;
        else
            return KTX_FILE_WRITE_ERROR;
    }

    return KTX_SUCCESS;
}

/**
 * @internal
 * @~English
 * @brief Get the current read/write position in a ktxFileStream.
 *
 * @param [in] str      pointer to the ktxStream to query.
 * @param [in,out] off  pointer to variable to receive the offset value.
 *
 * @return      KTX_SUCCESS on success, other KTX_* enum values on error.
 *
 * @exception KTX_INVALID_VALUE @p str or @p pos is @c NULL.
 */
static
KTX_error_code ktxFileStream_getpos(ktxStream* str, ktx_off_t* pos)
{
    if (!str || !pos)
        return KTX_INVALID_VALUE;
    
    assert(str->type == eStreamTypeFile);

    /* The cast quiets an Xcode warning when building for "Generic iOS Device".
     * For some reason, even when ARCHS is arm64, size_t is only a long. */
    *pos = (ktx_off_t)ftello(str->data.file);
    
    return KTX_SUCCESS;
}

/**
 * @internal
 * @~English
 * @brief Set the current read/write position in a ktxFileStream.
 *
 * Offset of 0 is the start of the file. This function operates
 * like Linux > 3.1's @c lseek() when it is passed a @c whence
 * of @c SEEK_DATA is it returns and error if the seek would
 * go beyond the end of the file.
 *
 * @param [in] str    pointer to the ktxStream whose r/w position is to be set.
 * @param [in] off    pointer to the offset value to set.
 *
 * @return      KTX_SUCCESS on success, other KTX_* enum values on error.
 *
 * @exception KTX_INVALID_VALUE @p str is @c NULL.
 * @exception KTX_INVALID_OPERATION @p pos is > the size of the file or an
 *                                  fseek error occurred.
 */
static
KTX_error_code ktxFileStream_setpos(ktxStream* str, ktx_off_t pos)
{
    ktx_size_t fileSize;
    
    if (!str)
        return KTX_INVALID_VALUE;

    assert(str->type == eStreamTypeFile);
    
    str->getsize(str, &fileSize);
    if (pos > fileSize)
        return KTX_INVALID_OPERATION;

    if (fseeko(str->data.file, pos, SEEK_SET) < 0)
        return KTX_FILE_SEEK_ERROR;
    
    return KTX_SUCCESS;
}

/**
 * @internal
 * @~English
 * @brief Get the size of a ktxFileStream in bytes.
 *
 * @param [in] str       pointer to the ktxStream whose size is to be queried.
 * @param [in,out] size  pointer to a variable in which size will be written.
 *
 * @return      KTX_SUCCESS on success, other KTX_* enum values on error.
 *
 * @exception KTX_INVALID_VALUE @p str or @p size is @c NULL.
 * @exception KTX_FILE_WRITE_ERROR a system error occurred while getting the
 *                                 size.
 */
static
KTX_error_code ktxFileStream_getsize(ktxStream* str, ktx_size_t* size)
{
    struct stat statbuf;

    if (!str || !size)
        return KTX_INVALID_VALUE;
    
    assert(str->type == eStreamTypeFile);
 
    if (fstat(fileno(str->data.file), &statbuf) < 0)
        return KTX_FILE_READ_ERROR;
    *size = (ktx_size_t)statbuf.st_size; /* See _getpos for why this cast. */
    
    return KTX_SUCCESS;
}

/**
 * @internal
 * @~English
 * @brief Initialize a ktxFileStream.
 *
 * @param [in] str      pointer to the ktxStream to initialize.
 * @param [in] file     pointer to the underlying FILE object.
 *
 * @return      KTX_SUCCESS on success, KTX_INVALID_VALUE on error.
 *
 * @exception KTX_INVALID_VALUE @p stream is @c NULL or @p file is @c NULL.
 */
KTX_error_code ktxFileStream_construct(ktxStream* str, FILE* file,
                                       ktx_bool_t closeFileOnDestruct)
{
    if (!str || !file)
        return KTX_INVALID_VALUE;

    str->data.file = file;
    str->type = eStreamTypeFile;
    str->read = ktxFileStream_read;
    str->skip = ktxFileStream_skip;
    str->write = ktxFileStream_write;
    str->getpos = ktxFileStream_getpos;
    str->setpos = ktxFileStream_setpos;
    str->getsize = ktxFileStream_getsize;
    str->destruct = ktxFileStream_destruct;
    str->closeOnDestruct = closeFileOnDestruct;

    return KTX_SUCCESS;
}

/**
 * @internal
 * @~English
 * @brief Destruct the stream, potentially closing the underlying FILE.
 *
 * This only closes the underyling FILE if the @c closeOnDestruct parameter to
 * ktxFileStream_construct() was not @c KTX_FALSE.
 *
 * @param [in] str pointer to the ktxStream whose FILE is to potentially
 *             be closed.
 */
void
ktxFileStream_destruct(ktxStream* str)
{
    assert(str && str->type == eStreamTypeFile);
    
    if (str->closeOnDestruct)
        fclose(str->data.file);
    str->data.file = 0;
}