Merge remote-tracking branch 'origin/master'

impl/stream.c

@@ -0,0 +1,303 @@
+/* Copyright (C) 2025 Aryadev Chavali
+
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the Unlicense for details.
+
+ * You may distribute and modify this code under the terms of the Unlicense,
+ * which you should have received a copy of along with this program.  If not,
+ * please go to <https://unlicense.org/>.
+
+ * Created: 2025-08-26
+ * Description: Stream implementation
+ */
+
+#include <string.h>
+
+#include <alisp.h>
+
+stream_err_t stream_init_string(stream_t *stream, char *name, sv_t contents)
+{
+  if (!stream)
+    return STREAM_ERR_INVALID_PTR;
+  name = name ? name : "<stream>";
+  memset(stream, 0, sizeof(*stream));
+
+  stream->type   = STREAM_TYPE_STRING;
+  stream->name   = name;
+  stream->string = contents;
+
+  return STREAM_ERR_OK;
+}
+
+stream_err_t stream_init_file(stream_t *stream, char *name, FILE *pipe)
+{
+  if (!stream || !pipe)
+    return STREAM_ERR_INVALID_PTR;
+  name = name ? name : "<stream>";
+  memset(stream, 0, sizeof(*stream));
+
+  stream->type      = STREAM_TYPE_FILE;
+  stream->name      = name;
+  stream->pipe.file = pipe;
+
+  vec_init(&stream->pipe.cache, STREAM_DEFAULT_CHUNK);
+  // try to read an initial chunk
+  stream_chunk(stream);
+
+  return STREAM_ERR_OK;
+}
+
+void stream_stop(stream_t *stream)
+{
+  if (!stream)
+    return;
+  switch (stream->type)
+  {
+  case STREAM_TYPE_STRING:
+    // Nothing to do, all dealt with outside of stream
+    break;
+  case STREAM_TYPE_FILE:
+    // Must cleanup vector
+    vec_free(&stream->pipe.cache);
+    break;
+  }
+  memset(stream, 0, sizeof(*stream));
+}
+
+u64 stream_size(stream_t *stream)
+{
+  assert(stream);
+  switch (stream->type)
+  {
+  case STREAM_TYPE_STRING:
+    return stream->string.size;
+  case STREAM_TYPE_FILE:
+    return stream->pipe.cache.size;
+  default:
+    FAIL("Unreachable");
+    return 0;
+  }
+}
+
+bool stream_eos(stream_t *stream)
+{
+  assert(stream);
+  switch (stream->type)
+  {
+  case STREAM_TYPE_STRING:
+    return stream->position >= stream->string.size;
+  case STREAM_TYPE_FILE:
+    return feof(stream->pipe.file);
+  default:
+    FAIL("Unreachable");
+    return 0;
+  }
+}
+
+bool stream_eoc(stream_t *stream)
+{
+  assert(stream);
+  switch (stream->type)
+  {
+  case STREAM_TYPE_STRING:
+    return stream->position >= stream->string.size;
+  case STREAM_TYPE_FILE:
+    return feof(stream->pipe.file) &&
+           stream->position >= stream->pipe.cache.size;
+  default:
+    FAIL("Unreachable");
+    return 0;
+  }
+}
+
+bool stream_chunk(stream_t *stream)
+{
+  assert(stream);
+  switch (stream->type)
+  {
+  case STREAM_TYPE_STRING:
+    // vacuously true
+    return true;
+  case STREAM_TYPE_FILE:
+  {
+    if (feof(stream->pipe.file))
+      return false;
+    vec_ensure_free(&stream->pipe.cache, STREAM_DEFAULT_CHUNK);
+    int read = fread(vec_data(&stream->pipe.cache) + stream->pipe.cache.size, 1,
+                     STREAM_DEFAULT_CHUNK, stream->pipe.file);
+    stream->pipe.cache.size += read;
+    return true;
+  }
+  default:
+    FAIL("Unreachable");
+    return 0;
+  }
+}
+
+char stream_next(stream_t *stream)
+{
+  char c = stream_peek(stream);
+  if (c != '\0')
+    ++stream->position;
+  return c;
+}
+
+char stream_peek(stream_t *stream)
+{
+  // If we've reached end of stream, and end of content, there's really nothing
+  // to check here.
+  if (stream_eoc(stream))
+    return '\0';
+
+  switch (stream->type)
+  {
+  case STREAM_TYPE_STRING:
+    return stream->string.data[stream->position];
+  case STREAM_TYPE_FILE:
+  {
+    // Cached already?  We are done.
+    if (stream->position < stream->pipe.cache.size)
+      return ((char *)vec_data(&stream->pipe.cache))[stream->position];
+
+    // Try to read chunks in till we've reached it or we're at the end of the
+    // file.
+    for (bool read_chunk = stream_chunk(stream);
+         read_chunk && stream->position >= stream->pipe.cache.size;
+         read_chunk = stream_chunk(stream))
+      continue;
+
+    // Same principle as the stream_eos(stream) check.
+    if (stream->position >= stream->pipe.cache.size)
+      return '\0';
+    return ((char *)vec_data(&stream->pipe.cache))[stream->position];
+  }
+  default:
+    FAIL("Unreachable");
+    return 0;
+  }
+}
+
+bool stream_seek(stream_t *stream, i64 offset)
+{
+  if (offset < 0)
+    return stream_seek_backward(stream, offset * -1);
+  else if (offset > 0)
+    return stream_seek_forward(stream, offset);
+  else
+    // vacuously successful
+    return true;
+}
+
+bool stream_seek_forward(stream_t *stream, u64 offset)
+{
+  if (stream_eoc(stream))
+    return false;
+
+  switch (stream->type)
+  {
+  case STREAM_TYPE_STRING:
+  {
+    if (stream->position + offset >= stream->string.size)
+      return false;
+
+    stream->position += offset;
+    return true;
+  }
+  case STREAM_TYPE_FILE:
+  {
+    // Similar principle as stream_peek really...
+
+    // Cached already?  We are done.
+    if (stream->position + offset < stream->pipe.cache.size)
+    {
+      stream->position += offset;
+      return true;
+    }
+
+    // Try to read chunks in till we've reached it or we're at the end of the
+    // file.
+    for (bool read_chunk = stream_chunk(stream);
+         read_chunk && stream->position + offset >= stream->pipe.cache.size;
+         read_chunk = stream_chunk(stream))
+      continue;
+
+    // Same principle as the stream_eoc(stream) check.
+    if (stream->position + offset >= stream->pipe.cache.size)
+      return false;
+    stream->position += offset;
+    return true;
+  }
+  default:
+    FAIL("Unreachable");
+    return 0;
+  }
+}
+
+bool stream_seek_backward(stream_t *stream, u64 offset)
+{
+  assert(stream);
+  if (stream->position < offset)
+    return false;
+  stream->position -= offset;
+  return true;
+}
+
+sv_t stream_substr(stream_t *stream, u64 size)
+{
+  if (stream_eoc(stream))
+    return SV(NULL, 0);
+
+  // TODO: this is kinda disgusting, any better way of doing this
+  u64 current_position = stream->position;
+  bool successful      = stream_seek_forward(stream, size);
+  // Reset the position in either situation
+  stream->position = current_position;
+
+  if (!successful)
+    return SV(NULL, 0);
+
+  char *ptr = NULL;
+  switch (stream->type)
+  {
+  case STREAM_TYPE_STRING:
+    ptr = stream->string.data;
+    break;
+  case STREAM_TYPE_FILE:
+    ptr = vec_data(&stream->pipe.cache);
+    break;
+  default:
+    FAIL("Unreachable");
+    return SV(NULL, 0);
+  }
+
+  return SV(ptr + stream->position, size);
+}
+
+sv_t stream_substr_abs(stream_t *stream, u64 index, u64 size)
+{
+  switch (stream->type)
+  {
+  case STREAM_TYPE_STRING:
+    if (index + size <= stream_size(stream))
+      return SV(stream->string.data + index, size);
+    return SV(NULL, 0);
+  case STREAM_TYPE_FILE:
+  {
+    if (index + size <= stream_size(stream))
+      return SV(vec_data(&stream->pipe.cache) + index, size);
+    // stream_size(stream) <= index + size => try reading chunks
+    for (bool read_chunk = stream_chunk(stream);
+         read_chunk && index + size >= stream->pipe.cache.size;
+         read_chunk = stream_chunk(stream))
+      continue;
+
+    if (index + size > stream_size(stream))
+      return SV(NULL, 0);
+    return SV(vec_data(&stream->pipe.cache) + index, size);
+  }
+  default:
+    assert("Unreachable");
+    return SV(NULL, 0);
+  }
+}