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_ringbuf.pyx
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_ringbuf.pyx
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# SPDX-License-Identifier: MIT
# Copyright (c) 2018, Mathias Laurin
"""A ring buffer.
See Also:
https://github.com/dhess/c-ringbuf/ Drew Hess' ring
buffer C implementation was a great help in the
development of this module.
"""
from libc.stdlib cimport malloc, free
from libc.string cimport memcpy
cimport mbedtls._ringbuf as _rb
import cython
cdef c_init(_rb.ring_buffer_ctx *ctx, size_t maxlen):
# ringbuf_new()
ctx._size = maxlen + 1
ctx.buf = <unsigned char *>malloc(ctx._size * sizeof(unsigned char))
if not ctx.buf:
raise MemoryError() # pragma: no cover
ctx.head = ctx.tail = ctx.buf
cdef void c_free(_rb.ring_buffer_ctx *ctx) nogil:
# ringbuf_free()
free(ctx.buf)
ctx.head = ctx.tail = NULL
cdef void c_clear(_rb.ring_buffer_ctx *ctx) nogil:
# ringbuf_reset()
ctx.head = ctx.tail
cdef size_t c_capacity(_rb.ring_buffer_ctx *ctx) nogil:
# ringbuf_capacity()
return ctx._size - 1
cdef unsigned char * c_end(ring_buffer_ctx * ctx) nogil:
# ringbuf_end()
return &ctx.buf[ctx._size]
cdef size_t c_len(ring_buffer_ctx *ctx) nogil:
# ringbuf_bytes_used()
if ctx.head >= ctx.tail:
return ctx.head - ctx.tail
else:
return c_capacity(ctx) - (ctx.tail - ctx.head - 1)
cdef c_peek(ring_buffer_ctx *ctx, size_t amt):
cdef unsigned char *dst = <unsigned char *>malloc(
min(amt, c_len(ctx) * sizeof(unsigned char)))
if not dst:
raise MemoryError() # pragma: no cover
try:
nread = c_peekinto(ctx, dst, amt)
return bytes(dst[:nread])
finally:
free(dst) # pragma: no cover
@cython.boundscheck(False)
cdef size_t c_peekinto(
ring_buffer_ctx *ctx, unsigned char *dst, size_t amt) nogil:
cdef size_t size = min(amt, c_len(ctx))
cdef size_t nread = 0
cdef unsigned char * index = ctx.tail
while nread != size:
if index == c_end(ctx):
index = ctx.buf
amt = min(<size_t>(c_end(ctx) - index), size - nread)
memcpy(&dst[nread], index, amt)
index += amt
nread += amt
return nread
cdef c_read(ring_buffer_ctx *ctx, size_t amt):
cdef unsigned char *dst = <unsigned char *>malloc(
min(amt, c_len(ctx)) * sizeof(unsigned char))
if not dst:
raise MemoryError() # pragma: no cover
try:
nread = c_readinto(ctx, dst, amt)
return bytes(dst[:nread])
finally:
free(dst) # pragma: no cover
@cython.boundscheck(False)
cdef size_t c_readinto(
ring_buffer_ctx *ctx, unsigned char *dst, size_t amt) nogil:
# ringbuf_memcpy_from()
cdef size_t size = min(amt, c_len(ctx))
cdef size_t nread = 0
while nread != size:
if ctx.tail == c_end(ctx):
ctx.tail = ctx.buf
amt = min(<size_t>(c_end(ctx) - ctx.tail), size - nread)
memcpy(&dst[nread], ctx.tail, amt)
ctx.tail += amt
nread += amt
return nread
cdef size_t c_consume(ring_buffer_ctx *ctx, size_t amt) nogil:
cdef size_t size = min(amt, c_len(ctx))
cdef size_t nconsumed = 0
while nconsumed != size:
if ctx.tail == c_end(ctx):
ctx.tail = ctx.buf
amt = min(<size_t>(c_end(ctx) - ctx.tail), size - nconsumed)
ctx.tail += amt
nconsumed += amt
return nconsumed
@cython.boundscheck(False)
cdef size_t c_write(
ring_buffer_ctx *ctx, const unsigned char *src, size_t amt) nogil:
# ringbuf_memcpy_into()
cdef size_t size = amt
# if size > c_capacity(ctx) - c_len(ctx):
# raise BufferError("Buffer overflow")
cdef size_t nwritten = 0
while nwritten != size:
if ctx.head == c_end(ctx):
ctx.head = ctx.buf
amt = min(<size_t>(c_end(ctx) - ctx.head), size - nwritten)
memcpy(ctx.head, &src[nwritten], amt)
ctx.head += amt
nwritten += amt
return nwritten
cdef class RingBuffer:
def __cinit__(self, size_t maxlen):
c_init(&self._ctx, maxlen)
def __dealloc__(self):
c_free(&self._ctx)
@property
def maxlen(self):
return c_capacity(&self._ctx)
def __eq__(self, other):
# Call `__bytes__()` directly for Python 2.7.
try:
return self.__bytes__() == other.__bytes__()
except AttributeError:
return self.__bytes__() == bytes(other)
def __len__(self):
return c_len(&self._ctx)
def __bool__(self):
return not self.empty()
def __bytes__(self):
return self.peek(len(self))
def clear(self):
c_clear(&self._ctx)
def full(self):
return len(self) == self.maxlen
def empty(self):
return len(self) == 0
def peek(self, size_t amt):
return c_peek(&self._ctx, amt)
def read(self, size_t amt):
return c_read(&self._ctx, amt)
def consume(self, size_t amt):
return c_consume(&self._ctx, amt)
def write(self, const unsigned char[:] src not None, amt=None):
if src.size == 0:
return 0
if amt is None:
amt = src.size
else:
amt = min(src.size, amt)
if amt > self.maxlen - len(self):
raise BufferError("Buffer overflow")
return c_write(&self._ctx, &src[0], amt)