使用其他文件系统函数实现fseek（）功能

我有一个自定义File system implementation for SD card . 见第没有14-16 . 该文件可由通过SPI接口与SD卡连接的微控制器读取或写入 .

我正在这个文件系统中存储BMP图像 . 但是应用程序需要从一个位置到另一个位置的大量随机跳转 .

我通过this answer了解到，我基本上需要fseek（） . 不幸的是，这个系统没有提供fseek（） . 可用的功能仅限于：

fcreate，fopen，fread，fwrite，feof，fclose：

是否可以使用可用的函数实现fseek（）或类似的功能？如果有，怎么样？如果没有，写低级（读取扇区等）代码是唯一的解决方案吗？

fcreate

Description: Creates a new file with the specified name.
Prototype: static BYTE fcreate (find_info* findinfo, char* filename)
Parameters: 
1. findinfo-Pointer to a structure with details about the file.
2. filename-Pointer to a memory location that contains the filename.
Return Value: 1, if the file was created successfully. 0, otherwise.

fopen

Description: Opens a file in one of three modes - Read (r), Write (w), Append (a). 
    In Write/Append modes, if the specified filename does not exist, it is created. 
    In   Write mode, if the specified file exists, it is overwritten.
    Prototype: int fopen (FILE* f, char* filename, char* mode)
    Parameters: 
    1. f-Pointer to file structure 
    2. filename-Pointer to a memory location that contains the filename.
    3. mode-Pointer to a memory location that contains the file open mode.
    Return Value: 1, if file was opened successfully. 0, otherwise.

fread

Description: Reads the specified number of bytes from a file.
Prototype: unsigned fread (FILE* f, BYTE* buffer, unsigned count)
Parameters: 
1. f-Pointer to file structure
2. buffer-Pointer to a memory locationwhere the data will be copied to.
3. count-The maximum number of bytes to read from the file.
Return Value: Number of bytes read from the file.

fwrite

Description: Writes the specified number of bytes to a file.
Prototype: unsigned fwrite (FILE* f, BYTE* buffer, unsigned count)
Parameters: 
1. f-Pointer to file structure
2. buffer-Pointer to a memory location where the data will be copied from.
3. count-The number of bytes to write to the file.
Return Value: Number of bytes written to the file.

feof

Description: Checks whether the specified file's current position pointer has reached the end of the file.
Prototype: int feof (FILE* f)
Parameters: 
1. f-Pointer to file structure
Return Value: 0, if the file'scurrent position pointer has not reached the end of the file.    1, if the file's current position pointer has reached the end of the file.

fclose

Description: Closes a file.
Prototype: void fclose (FILE* f)
Parameters: 1. f-Pointer to file structure
Return Value: None.