From 4e09bca9e34c226b6d7e34b4fa11248405fd988e Mon Sep 17 00:00:00 2001
From: Anton Kling <anton@kling.gg>
Date: Sun, 22 Oct 2023 19:50:38 +0200
Subject: Move everything into a new repo.

---
 userland/libc/stdio/open_memstream.c | 108 +++++++++++++++++++++++++++++++++++
 1 file changed, 108 insertions(+)
 create mode 100644 userland/libc/stdio/open_memstream.c

(limited to 'userland/libc/stdio/open_memstream.c')

diff --git a/userland/libc/stdio/open_memstream.c b/userland/libc/stdio/open_memstream.c
new file mode 100644
index 0000000..8f359b9
--- /dev/null
+++ b/userland/libc/stdio/open_memstream.c
@@ -0,0 +1,108 @@
+#include <assert.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+/*
+struct __IO_FILE {
+  size_t (*write)(FILE *, const unsigned char *, size_t);
+  size_t (*read)(FILE *, unsigned char *, size_t);
+  int (*seek)(FILE *, long, int);
+  long offset_in_file;
+  int buffered_char;
+  int has_buffered_char;
+  int fd;
+  uint8_t is_eof;
+  uint8_t has_error;
+  uint64_t file_size;
+  void *cookie;
+};
+*/
+
+struct Memstream {
+  size_t buffer_usage;
+  char *buffer;
+};
+
+#define MEMSTREAM_DEF_SIZE 4096
+
+size_t memstream_write(FILE *fp, const unsigned char *buf, size_t n) {
+  struct Memstream *c = fp->cookie;
+  // FIXME: Do a reallocation
+  if (c->buffer_usage + n >= fp->file_size) {
+    n = fp->file_size - c->buffer_usage;
+  }
+
+  memcpy(c->buffer + fp->offset_in_file, buf, n);
+  fp->offset_in_file += n;
+  if (fp->offset_in_file > c->buffer_usage)
+    c->buffer_usage = fp->offset_in_file;
+  return n;
+}
+
+size_t memstream_read(FILE *fp, unsigned char *buf, size_t n) {
+  struct Memstream *c = fp->cookie;
+  size_t length_left = c->buffer_usage - fp->offset_in_file;
+  n = min(length_left, n);
+  memcpy(buf, c->buffer + fp->offset_in_file, n);
+  fp->offset_in_file += n;
+  if (0 == n)
+    fp->is_eof = 1;
+  return n;
+}
+
+int memstream_seek(FILE *stream, long offset, int whence) {
+  switch (whence) {
+  case SEEK_SET:
+    stream->offset_in_file = offset;
+    break;
+  case SEEK_CUR:
+    stream->offset_in_file += offset;
+    break;
+  case SEEK_END:
+    stream->offset_in_file = stream->file_size + offset;
+    break;
+  default:
+    assert(0);
+    break;
+  }
+  // FIXME: Error checking
+  return 0;
+}
+
+FILE *open_memstream(char **bufp, size_t *sizep) {
+  struct Memstream *c = NULL;
+  FILE *fp = malloc(sizeof(FILE));
+  if (!fp)
+    return NULL;
+
+  fp->offset_in_file = 0;
+  fp->buffered_char = 0;
+  fp->has_buffered_char = 0;
+  fp->seek = memstream_seek;
+  fp->fd = -1;
+  fp->is_eof = 0;
+  fp->has_error = 0;
+  fp->file_size = MEMSTREAM_DEF_SIZE;
+
+  fp->write = memstream_write;
+  fp->read = memstream_read;
+
+  c = malloc(sizeof(struct Memstream));
+  if (!c) {
+    goto _exit_memstream_fail;
+  }
+
+  fp->cookie = (void *)c;
+
+  c->buffer = *bufp = malloc(MEMSTREAM_DEF_SIZE);
+  if (!bufp) {
+    goto _exit_memstream_fail;
+  }
+  c->buffer_usage = 0;
+
+  return fp;
+_exit_memstream_fail:
+  free(c);
+  free(fp);
+  return NULL;
+}
-- 
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