I had a look now at fgets/fgetc, it is not keeping track of position
with a static variable.
It is hidden in FILE struct:
struct __stdio_file {
unsigned char *bufpos; /* the next byte to write to or read from */
unsigned char *bufread; /* the end of data returned by last read() */
unsigned char *bufwrite; /* highest address writable by macro */
unsigned char *bufstart; /* the start of the buffer */
unsigned char *bufend; /* the end of the buffer; ie the byte after
the last
malloc()ed byte */
int fd; /* the file descriptor associated with the stream */
int mode;
char unbuf[8]; /* The buffer for 'unbuffered' streams */
struct __stdio_file * next;
};
(example from dev86/bcc)
Nils
-------- Forwarded Message --------
Subject:
Re: [Freedos-user] Preloading text files in C
Date:
Thu, 10 Jan 2019 06:34:01 +0100
From:
stecdose <[email protected]>
To:
[email protected]
Hi Ken and TK Chia,
fmemopen looks very good, but sadly not available in Watcom. This is not
a big problem, rewriting the code to use buffers is not that much work.
I am using a own putc/puts-function-pair, which directly writes to video
memory. This lets me easily change it to another data source. I "saved"
fmemopen to my list of things to remember for future projects.
I will implement it similar to this:
int number;
char linebuf[81];
number = preload("filename.txt");
...
while(get_line_from_buffer(number, &linebuf, 81) != NULL) {
do_something();
}
I'll havea look at fgets how this one is storing the position in file
and do it this way. I assume it is a static or global variable keeping
track of position. I had a look at different fmemopen implementations
and there's a lot of stuff I do not totally understand...
Thank you very much to both of you!
Nils
On 1/9/19 3:35 PM, TK Chia wrote:
Hello Nils, hello Ken,
ptr_array[0] = malloc(size_of_textfile);
copy_to(file0, ptr_array[0];
ptr_array[1] = malloc(size_of_textfile);
copy_to(file1, ptr_array[1];
...
Can I still use fgets() on these pointers once the file has been loaded
there?
No, fgets wants a FILE *, which is a pointer to a stream, not a char *.
If you are not able to rewrite the program to process the buffer
directly, forgetting about fgets(), there is fmemopen() which returns a
FILE * given a string. But it may not be implemented in your C library.
https://pubs.opengroup.org/onlinepubs/9699919799/functions/fmemopen.html
I just found that the Newlib library as included in the gcc-ia16
toolchain does happen to implement fmemopen( ) (and several other
POSIX functions as well).
However, Open Watcom's C library does not have this function.
I suppose, if a `FILE *' is not absolutely needed, then one can use
strchr( ), strcspn( ), etc. to slice the input up into separate lines,
without writing a lot of code.
Thank you!
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