Operating System Interface

Detailed Description

The MeatAxe is written for a UNIX-like operating environment and uses many functions of the standard C library. To make the MeatAxe more portable between different operating systems, some C library and system calls are accessed through wrapper functions. These wrapper functions have names that begin with 'Sys'. For example SysFree() is the wrapper function for free().

Macros
#define	FM_READ   0x01
	File mode: read.
#define	FM_CREATE   0x02
	File mode: write.
#define	FM_APPEND   0x03
	File mode: append.

Functions
void	SysInit ()
	OS-specific initialization. More...
long	SysTimeUsed (void)
	CPU time. More...
void	SysSetTimeLimit (long nsecs)
	Set CPU time limit. More...
FILE *	SysFopen (const char *name, int mode)
	Open a file. More...
int	SysFseek (FILE *file, long pos)
	Set file pointer. More...
int	SysRemoveFile (const char *name)
	Remove a file This function deletes a file. More...
int	SysRemoveDirectory (const char *name)
	Remove a directory. More...
int	SysCreateDirectory (const char *name)
	Create a directory. More...
int	SysFseekRelative (FILE *file, long distance)
	Set file pointer relative to current position. More...
void *	SysMalloc (size_t nbytes)
	Allocate memory. More...
void *	SysRealloc (void *buf, size_t nbytes)
	Resize memory block. More...
void	SysFree (void *x)
	Free memory block. More...
int	SysGetPid ()
	Get process id. More...

Function Documentation

SysCreateDirectory()

int SysCreateDirectory

(

const char *

name

)

Create a directory.

This function creates a new directory. If the directory cannot be created for some reason, a run-time error is generated and the function returns -1.

See also

SysRemoveDirectory()

Parameters

name	Name of the directory.

Returns

0 on success, -1 on error.

SysFopen()

FILE* SysFopen	(	const char *	name,
		int	mode
	)

Open a file.

This function opens a file, like fopen(). The second argument, must be one of the predfined constants FM_READ (open for reading), FM_CREAT (create a new file and open for writing, or FM_APPEND (append to existing file or create a new file). Additional flags may be or'ed to the mode:

FM_LIB

If the file does not exist in the current directory, look in the library directory. The library directory is defined either by the environment variable MTXLIB, or at compile-time by the macro MTXLIB.

FM_TEXT

Open in text mode. This flag must be used on some systems (e.g., MS-DOS) to open text files. By default, files are assumed to contain binary data.

FM_NOERROR

Do not generate an error if the file does not exist.

See also

FfReadHeader() FfWriteHeader()

Returns

A pointer to the open file or NULL on error.

SysFree()

void SysFree

(

void *

x

)

Free memory block.

This function works like free() but checks if the argument is not NULL. Otherwise, an appropriate error message is generated.

Parameters

x	Pointer to the memory block.

SysFseek()

int SysFseek	(	FILE *	file,
		long	pos
	)

Set file pointer.

This function sets the file pointer to a given position. If pos is greater than or equal to zero, it is interpreted as an absolute position (relative to start of file). If pos is negative, the file pointer is moved to the end of file.

See also

SysFseekRelative(), FfSeekRow()

Parameters

file	File handle.
pos	New position of file pointer.

Returns

0 on success, nonzero otherwise.

SysFseekRelative()

int SysFseekRelative	(	FILE *	file,
		long	distance
	)

Set file pointer relative to current position.

This function moves the file pointer by a given number of bytes, which may be positive or negative.

Parameters

file	The file handle.
distance	The number of bytes by which the file pointer shall be moved.

Returns

0 on success, nonzero on error.

See also

SysFseek(), FfSeekRow()

SysGetPid()

int SysGetPid

(

)

Get process id.

This function returns a number which uniquely identifies the calling process on the local system. The exact meaning of this number depends on the operating system. In an UNIX environment, it is the process id (PID).

Returns

Process id.

SysInit()

void SysInit

(

void

)

OS-specific initialization.

This function is called during library initialization. It performs any OS-specific actions. Applications should never call this function directly. Use MtxInit() instead.

SysMalloc()

void* SysMalloc

(

size_t

nbytes

)

Allocate memory.

This function works like malloc(), but the return value is never 0, even when the function was called with a 0 argument.

Parameters

nbytes

Size of memory block to allocate.

Returns

Pointer to memory block or NULL on error.

SysRealloc()

void* SysRealloc	(	void *	buf,
		size_t	nbytes
	)

Resize memory block.

This function works like realloc() but handles zero-length blocks differently (namely, by allocating 1 byte instead) to avoid problems with broken realloc() implementations.

Parameters

buf	Pointer to memory block.
nbytes	Desired new size.

Returns

Pointer to resized memory block or NULL on error.

SysRemoveDirectory()

int SysRemoveDirectory

(

const char *

name

)

Remove a directory.

This function removes the specified directory.

See also

SysCreateDirectory().

Parameters

name	Name of the directory.

Returns

0 on success, -1 on error.

SysRemoveFile()

int SysRemoveFile

(

const char *

name

)

Remove a file This function deletes a file.

On a UNIX system, SysRemoveFile() just calls remove(). If the file to be deleted does not exist or cannot be removed for some other reason, run-time error error is generated.

SysSetTimeLimit()

void SysSetTimeLimit

(

long

nsecs

)

Set CPU time limit.

This function sets a CPU time limit for the calling process. When the limit is exceeded the process is killed.

Parameters

nsecs

CPU time limit in seconds.

Attention

This function is not available on all platforms.

SysTimeUsed()

long SysTimeUsed

(

void

)

CPU time.

This function returns the CPU time used by the calling process in units of 1/10 seconds.

See also

SysSetTimeLimit()

Returns

CPU time used.