/**

* Copyright (c) 2016-present, Gregory Szorc

* All rights reserved.

*

* This software may be modified and distributed under the terms

* of the BSD license. See the LICENSE file for details.

*/

#include "python-zstandard.h"

#define min(a, b) (((a) < (b)) ? (a) : (b))

extern PyObject* ZstdError;

PyDoc_STRVAR(ZstdCompressorIterator__doc__,

"Represents an iterator of compressed data.\n"

);

static void ZstdCompressorIterator_dealloc(ZstdCompressorIterator* self) {

	Py_XDECREF(self->readResult);

	Py_XDECREF(self->compressor);

	Py_XDECREF(self->reader);

	if (self->buffer.buf) {

		PyBuffer_Release(&self->buffer);

		memset(&self->buffer, 0, sizeof(self->buffer));

	}

	if (self->output.dst) {

		PyMem_Free(self->output.dst);

		self->output.dst = NULL;

	}

	PyObject_Del(self);

}

static PyObject* ZstdCompressorIterator_iter(PyObject* self) {

	Py_INCREF(self);

	return self;

}

static PyObject* ZstdCompressorIterator_iternext(ZstdCompressorIterator* self) {

	size_t zresult;

	PyObject* readResult = NULL;

	PyObject* chunk;

	char* readBuffer;

	Py_ssize_t readSize = 0;

	Py_ssize_t bufferRemaining;

	if (self->finishedOutput) {

		PyErr_SetString(PyExc_StopIteration, "output flushed");

		return NULL;

	}

feedcompressor:

	/* If we have data left in the input, consume it. */

	if (self->input.pos < self->input.size) {

		Py_BEGIN_ALLOW_THREADS

		zresult = ZSTD_compressStream2(self->compressor->cctx, &self->output,

			&self->input, ZSTD_e_continue);

		Py_END_ALLOW_THREADS

		/* Release the Python object holding the input buffer. */

		if (self->input.pos == self->input.size) {

			self->input.src = NULL;

			self->input.pos = 0;

			self->input.size = 0;

			Py_DECREF(self->readResult);

			self->readResult = NULL;

		}

		if (ZSTD_isError(zresult)) {

			PyErr_Format(ZstdError, "zstd compress error: %s", ZSTD_getErrorName(zresult));

			return NULL;

		}

		/* If it produced output data, emit it. */

		if (self->output.pos) {

			chunk = PyBytes_FromStringAndSize(self->output.dst, self->output.pos);

			self->output.pos = 0;

			return chunk;

		}

	}

	/* We should never have output data sitting around after a previous call. */

	assert(self->output.pos == 0);

	/* The code above should have either emitted a chunk and returned or consumed

	the entire input buffer. So the state of the input buffer is not

	relevant. */

	if (!self->finishedInput) {

		if (self->reader) {

			readResult = PyObject_CallMethod(self->reader, "read", "I", self->inSize);

			if (!readResult) {

				PyErr_SetString(ZstdError, "could not read() from source");

				return NULL;

			}

			PyBytes_AsStringAndSize(readResult, &readBuffer, &readSize);

		}

		else {

			assert(self->buffer.buf);

			/* Only support contiguous C arrays. */

			assert(self->buffer.strides == NULL && self->buffer.suboffsets == NULL);

			assert(self->buffer.itemsize == 1);

			readBuffer = (char*)self->buffer.buf + self->bufferOffset;

			bufferRemaining = self->buffer.len - self->bufferOffset;

			readSize = min(bufferRemaining, (Py_ssize_t)self->inSize);

			self->bufferOffset += readSize;

		}

		if (0 == readSize) {

			Py_XDECREF(readResult);

			self->finishedInput = 1;

		}

		else {

			self->readResult = readResult;

		}

	}

	/* EOF */

	if (0 == readSize) {

		self->input.src = NULL;

		self->input.size = 0;

		self->input.pos = 0;

		zresult = ZSTD_compressStream2(self->compressor->cctx, &self->output,

			&self->input, ZSTD_e_end);

		if (ZSTD_isError(zresult)) {

			PyErr_Format(ZstdError, "error ending compression stream: %s",

				ZSTD_getErrorName(zresult));

			return NULL;

		}

		assert(self->output.pos);

		if (0 == zresult) {

			self->finishedOutput = 1;

		}

		chunk = PyBytes_FromStringAndSize(self->output.dst, self->output.pos);

		self->output.pos = 0;

		return chunk;

	}

	/* New data from reader. Feed into compressor. */

	self->input.src = readBuffer;

	self->input.size = readSize;

	self->input.pos = 0;

	Py_BEGIN_ALLOW_THREADS

	zresult = ZSTD_compressStream2(self->compressor->cctx, &self->output,

		&self->input, ZSTD_e_continue);

	Py_END_ALLOW_THREADS

	/* The input buffer currently points to memory managed by Python

	(readBuffer). This object was allocated by this function. If it wasn't

	fully consumed, we need to release it in a subsequent function call.

	If it is fully consumed, do that now.

	*/

	if (self->input.pos == self->input.size) {

		self->input.src = NULL;

		self->input.pos = 0;

		self->input.size = 0;

		Py_XDECREF(self->readResult);

		self->readResult = NULL;

	}

	if (ZSTD_isError(zresult)) {

		PyErr_Format(ZstdError, "zstd compress error: %s", ZSTD_getErrorName(zresult));

		return NULL;

	}

	assert(self->input.pos <= self->input.size);

	/* If we didn't write anything, start the process over. */

	if (0 == self->output.pos) {

		goto feedcompressor;

	}

	chunk = PyBytes_FromStringAndSize(self->output.dst, self->output.pos);

	self->output.pos = 0;

	return chunk;

}

PyTypeObject ZstdCompressorIteratorType = {

	PyVarObject_HEAD_INIT(NULL, 0)

	"zstd.ZstdCompressorIterator",   /* tp_name */

	sizeof(ZstdCompressorIterator),  /* tp_basicsize */

	0,                               /* tp_itemsize */

	(destructor)ZstdCompressorIterator_dealloc, /* tp_dealloc */

	0,                               /* tp_print */

	0,                               /* tp_getattr */

	0,                               /* tp_setattr */

	0,                               /* tp_compare */

	0,                               /* tp_repr */

	0,                               /* tp_as_number */

	0,                               /* tp_as_sequence */

	0,                               /* tp_as_mapping */

	0,                               /* tp_hash */

	0,                               /* tp_call */

	0,                               /* tp_str */

	0,                               /* tp_getattro */

	0,                               /* tp_setattro */

	0,                               /* tp_as_buffer */

	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE, /* tp_flags */

	ZstdCompressorIterator__doc__,   /* tp_doc */

	0,                               /* tp_traverse */

	0,                               /* tp_clear */

	0,                               /* tp_richcompare */

	0,                               /* tp_weaklistoffset */

	ZstdCompressorIterator_iter,     /* tp_iter */

	(iternextfunc)ZstdCompressorIterator_iternext, /* tp_iternext */

	0,                               /* tp_methods */

	0,                               /* tp_members */

	0,                               /* tp_getset */

	0,                               /* tp_base */

	0,                               /* tp_dict */

	0,                               /* tp_descr_get */

	0,                               /* tp_descr_set */

	0,                               /* tp_dictoffset */

	0,                               /* tp_init */

	0,                               /* tp_alloc */

	PyType_GenericNew,              /* tp_new */

};

void compressoriterator_module_init(PyObject* mod) {

	Py_SET_TYPE(&ZstdCompressorIteratorType, &PyType_Type);

	if (PyType_Ready(&ZstdCompressorIteratorType) < 0) {

		return;

	}

}