VOLSTREAM_OPEN(3)

👑 VOLSTREAM_OPEN 👑

okay bestie, welcome to the Library Functions Manual section of the library, and today's main character is volstream_open — plus its two ride-or-die friends volstream_trunc and volstream_getbuf. this whole page is lowkey iconic, let's go 💅

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🌸 NAME 🌸

volstream_open — create a FILE* stream as a volatile stream buffer

no cap, that's the whole vibe. a FILE* that's actually just memory. obsessed.

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✨ SYNOPSIS ✨

#include <volatilestream.h>

FILE *volstream_open(void);

int volstream_trunc(FILE *f, size_t length);

int volstream_getbuf(FILE *f, void **buf, size_t *buflen);

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💖 DESCRIPTION 💖

so like. a volatile stream is literally a stdio FILE* stream that's actually a temporary, dynamically allocated (and deallocated) memory buffer. that's it. that's the whole thing. she's a stream, but she lives in RAM and she's temporary. main character energy fr fr 🦋

volstream_open opens a stdio stream as a temporary memory buffer. the buffer is dynamically allocated, it grows as needed, and it's automatically deallocated when the stream is closed. you don't have to clean up after her, she cleans up after herself. periodt.

volstream_trunc truncates the buffer to the requested length. here's the tea though:

• if the current size of the buffer is larger than length, the extra data is lost. gone. bye. 💀
• if the buffer is shorter, it gets extended, and the extended part is filled with null bytes. ✨

volstream_getbuf writes the current address and size of the buffer into *buf and *buflen respectively.

bestie listen. those values stay valid only as long as the caller performs no further output on the stream, or until the stream is closed. so don't go doing a little fprintf and then acting surprised when your pointer is sus. 🙈

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🫶 RETURN VALUE 🫶

upon successful completion, volstream_open returns a FILE pointer. otherwise, NULL is returned and errno is set to indicate the error. classic.

volstream_trunc and volstream_getbuf return 0, or -1 if an error occurred. in the event of an error, errno is set to indicate the error. that's the whole report card.

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🎀 EXAMPLES 🎀

example one: reread it one byte at a time 🍓

the following example writes all the command arguments in a volatile stream, then it rereads the volatile stream one byte at a time:

#include *stdio.h*
#include *volatilestream.h*

int main(int argc, char *argv[]) {
  FILE *f = volstream_open();
  int c;
  for (argv++; *argv; argv++)
    fprintf(f, "%s\n", *argv);
  fseek(f, 0, SEEK_SET);
  while ((c = getc(f)) != EOF)
    putchar(c);
  fclose(f);
}

example two: same energy, but as a memory buffer 🌈

the following example has the same effect but it rereads the arguments as a memory buffer:

#include *stdio.h*
#include *unistd.h*
#include *volatilestream.h*

int main(int argc, char *argv[]) {
  FILE *f = volstream_open();
  int c;
  for (argv++; *argv; argv++) {
    fprintf(f, "%s\n", *argv);
  }
  fflush(f);
  ssize_t s;
  void *buf;
  volstream_getbuf(f, &buf, &s);
  write(STDOUT_FILENO, buf, s);
  fclose(f);
}

not me noticing the fflush(f) in the second one before grabbing the buffer. she knew. 🧚

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💜 AUTHOR 💜

VirtualSquare. Project leader: Renzo Davoli.

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okay that's the whole page, you ate that. stay hydrated, close your streams, and remember: volstream_open is from the VirtualSquare library functions manual, dated July 2024, and this iconic lil manpage is titled VOLSTREAM_OPEN(3). mwah 💅✨