Add simple growable buffer implementation

1 files changed, 43 insertions, 0 deletions

diff --git a/buffer.c b/buffer.c
new file mode 100644
index 0000000..71d51f8
--- /dev/null
+++ b/buffer.c
@@ -0,0 +1,43 @@
+#include "buffer.h"
+
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <unistd.h>
+
+void BufferCreate(struct Buffer* buffer) {
+  memset(buffer, 0, sizeof(struct Buffer));
+}
+
+void* BufferReserve(struct Buffer* buffer, size_t size) {
+  size_t alloc = buffer->size + size;
+  if (alloc > buffer->alloc) {
+    void* data = realloc(buffer->data, alloc);
+    if (!data) return NULL;
+    buffer->data = data;
+    buffer->alloc = alloc;
+  }
+  return (char*)buffer->data + buffer->size;
+}
+
+int BufferAppendFrom(struct Buffer* buffer, int fd) {
+  int nbytes;
+  if (ioctl(fd, FIONREAD, &nbytes) == -1) return -1;
+  if (!nbytes) return 0;
+  void* data = BufferReserve(buffer, (size_t)nbytes);
+  if (!data) return -1;
+  ssize_t result = read(fd, data, (size_t)nbytes);
+  if (result > 0) buffer->size += (size_t)result;
+  return (int)result;
+}
+
+void BufferDiscard(struct Buffer* buffer, size_t size) {
+  size_t tail_size = buffer->size - size;
+  if (tail_size) {
+    const char* tail = (const char*)buffer->data + size;
+    memmove(buffer->data, tail, tail_size);
+  }
+  buffer->size = tail_size;
+}
+
+void BufferDestroy(struct Buffer* buffer) { free(buffer->data); }