feat: Include dictionary member in `ArrowArrayView` struct (#221)

This doesn't add any features really, but ensures that one can walk
`ArrowSchema`, `ArrowArray`, and `ArrowArrayView` recursively using the
same pattern. I'd like to include this in the 0.2 release because it is
very difficult to work around this limitation: for example, if you have
a deeply nested dictionary field, you currently have to walk your whole
tree of arrays twice (once to validate the non-dictionary bits, once
looking for dictionary bits that may or may not exist to validate). The
R package worked around this in some creative but error-prone ways and
I'd like to avoid anybody else attempting creative workarounds when this
is a feature that will almost certainly get added soon.

Another application of this is device array support, since that PR
essentially constructs an `ArrowArrayView` and recursively copies the
buffer view from the array view to a standalone buffer using some
device-specific logic.
8 files changed
tree: f70a537a7d0e2b931eaeae6b0360c4959f70dc24
  1. .github/
  2. ci/
  3. dev/
  4. dist/
  5. docs/
  6. examples/
  7. extensions/
  8. python/
  9. r/
  10. src/
  11. .asf.yaml
  12. .clang-format
  13. .env
  14. .gitattributes
  15. .gitignore
  16. CHANGELOG.md
  17. CMakeLists.txt
  18. CMakePresets.json
  19. CMakeUserPresets.json.example
  20. docker-compose.yml
  21. LICENSE.txt
  22. NOTICE.txt
  23. README.md
  24. valgrind.supp
README.md

nanoarrow

Codecov test coverage Documentation nanoarrow on GitHub

The nanoarrow library is a set of helper functions to interpret and generate Arrow C Data Interface and Arrow C Stream Interface structures. The library is in active early development and users should update regularly from the main branch of this repository.

Whereas the current suite of Arrow implementations provide the basis for a comprehensive data analysis toolkit, this library is intended to support clients that wish to produce or interpret Arrow C Data and/or Arrow C Stream structures where linking to a higher level Arrow binding is difficult or impossible.

Using the C library

The nanoarrow C library is intended to be copied and vendored. This can be done using CMake or by using the bundled nanoarrow.h/nanorrow.c distribution available in the dist/ directory in this repository. Examples of both can be found in the examples/ directory in this repository.

A simple producer example:

#include "nanoarrow.h"

int make_simple_array(struct ArrowArray* array_out, struct ArrowSchema* schema_out) {
  struct ArrowError error;
  array_out->release = NULL;
  schema_out->release = NULL;

  NANOARROW_RETURN_NOT_OK(ArrowArrayInitFromType(array_out, NANOARROW_TYPE_INT32));

  NANOARROW_RETURN_NOT_OK(ArrowArrayStartAppending(array_out));
  NANOARROW_RETURN_NOT_OK(ArrowArrayAppendInt(array_out, 1));
  NANOARROW_RETURN_NOT_OK(ArrowArrayAppendInt(array_out, 2));
  NANOARROW_RETURN_NOT_OK(ArrowArrayAppendInt(array_out, 3));
  NANOARROW_RETURN_NOT_OK(ArrowArrayFinishBuildingDefault(array_out, &error));

  NANOARROW_RETURN_NOT_OK(ArrowSchemaInit(schema_out, NANOARROW_TYPE_INT32));

  return NANOARROW_OK;
}

A simple consumer example:

#include <stdio.h>

#include "nanoarrow.h"

int print_simple_array(struct ArrowArray* array, struct ArrowSchema* schema) {
  struct ArrowError error;
  struct ArrowArrayView array_view;
  NANOARROW_RETURN_NOT_OK(ArrowArrayViewInitFromSchema(&array_view, schema, &error));

  if (array_view.storage_type != NANOARROW_TYPE_INT32) {
    printf("Array has storage that is not int32\n");
  }

  int result = ArrowArrayViewSetArray(&array_view, array, &error);
  if (result != NANOARROW_OK) {
    ArrowArrayViewReset(&array_view);
    return result;
  }

  for (int64_t i = 0; i < array->length; i++) {
    printf("%d\n", (int)ArrowArrayViewGetIntUnsafe(&array_view, i));
  }

  ArrowArrayViewReset(&array_view);
  return NANOARROW_OK;
}