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/**
* Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
* SPDX-License-Identifier: Apache-2.0.
*/
#include <aws/common/ring_buffer.h>
#include <aws/common/byte_buf.h>
#ifdef CBMC
# define AWS_ATOMIC_LOAD_PTR(ring_buf, dest_ptr, atomic_ptr, memory_order) \
dest_ptr = aws_atomic_load_ptr_explicit(atomic_ptr, memory_order); \
assert(__CPROVER_same_object(dest_ptr, ring_buf->allocation)); \
assert(aws_ring_buffer_check_atomic_ptr(ring_buf, dest_ptr));
# define AWS_ATOMIC_STORE_PTR(ring_buf, atomic_ptr, src_ptr, memory_order) \
assert(aws_ring_buffer_check_atomic_ptr(ring_buf, src_ptr)); \
aws_atomic_store_ptr_explicit(atomic_ptr, src_ptr, memory_order);
#else
# define AWS_ATOMIC_LOAD_PTR(ring_buf, dest_ptr, atomic_ptr, memory_order) \
dest_ptr = aws_atomic_load_ptr_explicit(atomic_ptr, memory_order);
# define AWS_ATOMIC_STORE_PTR(ring_buf, atomic_ptr, src_ptr, memory_order) \
aws_atomic_store_ptr_explicit(atomic_ptr, src_ptr, memory_order);
#endif
#define AWS_ATOMIC_LOAD_TAIL_PTR(ring_buf, dest_ptr) \
AWS_ATOMIC_LOAD_PTR(ring_buf, dest_ptr, &(ring_buf)->tail, aws_memory_order_acquire);
#define AWS_ATOMIC_STORE_TAIL_PTR(ring_buf, src_ptr) \
AWS_ATOMIC_STORE_PTR(ring_buf, &(ring_buf)->tail, src_ptr, aws_memory_order_release);
#define AWS_ATOMIC_LOAD_HEAD_PTR(ring_buf, dest_ptr) \
AWS_ATOMIC_LOAD_PTR(ring_buf, dest_ptr, &(ring_buf)->head, aws_memory_order_relaxed);
#define AWS_ATOMIC_STORE_HEAD_PTR(ring_buf, src_ptr) \
AWS_ATOMIC_STORE_PTR(ring_buf, &(ring_buf)->head, src_ptr, aws_memory_order_relaxed);
int aws_ring_buffer_init(struct aws_ring_buffer *ring_buf, struct aws_allocator *allocator, size_t size) {
AWS_PRECONDITION(ring_buf != NULL);
AWS_PRECONDITION(allocator != NULL);
AWS_PRECONDITION(size > 0);
AWS_ZERO_STRUCT(*ring_buf);
ring_buf->allocation = aws_mem_acquire(allocator, size);
if (!ring_buf->allocation) {
return AWS_OP_ERR;
}
ring_buf->allocator = allocator;
aws_atomic_init_ptr(&ring_buf->head, ring_buf->allocation);
aws_atomic_init_ptr(&ring_buf->tail, ring_buf->allocation);
ring_buf->allocation_end = ring_buf->allocation + size;
AWS_POSTCONDITION(aws_ring_buffer_is_valid(ring_buf));
return AWS_OP_SUCCESS;
}
void aws_ring_buffer_clean_up(struct aws_ring_buffer *ring_buf) {
AWS_PRECONDITION(aws_ring_buffer_is_valid(ring_buf));
if (ring_buf->allocation) {
aws_mem_release(ring_buf->allocator, ring_buf->allocation);
}
AWS_ZERO_STRUCT(*ring_buf);
}
int aws_ring_buffer_acquire(struct aws_ring_buffer *ring_buf, size_t requested_size, struct aws_byte_buf *dest) {
AWS_PRECONDITION(aws_ring_buffer_is_valid(ring_buf));
AWS_PRECONDITION(aws_byte_buf_is_valid(dest));
AWS_ERROR_PRECONDITION(requested_size != 0);
uint8_t *tail_cpy;
uint8_t *head_cpy;
AWS_ATOMIC_LOAD_TAIL_PTR(ring_buf, tail_cpy);
AWS_ATOMIC_LOAD_HEAD_PTR(ring_buf, head_cpy);
/* this branch is, we don't have any vended buffers. */
if (head_cpy == tail_cpy) {
size_t ring_space = ring_buf->allocation_end == NULL ? 0 : ring_buf->allocation_end - ring_buf->allocation;
if (requested_size > ring_space) {
AWS_POSTCONDITION(aws_ring_buffer_is_valid(ring_buf));
AWS_POSTCONDITION(aws_byte_buf_is_valid(dest));
return aws_raise_error(AWS_ERROR_OOM);
}
AWS_ATOMIC_STORE_HEAD_PTR(ring_buf, ring_buf->allocation + requested_size);
AWS_ATOMIC_STORE_TAIL_PTR(ring_buf, ring_buf->allocation);
*dest = aws_byte_buf_from_empty_array(ring_buf->allocation, requested_size);
AWS_POSTCONDITION(aws_ring_buffer_is_valid(ring_buf));
AWS_POSTCONDITION(aws_byte_buf_is_valid(dest));
return AWS_OP_SUCCESS;
}
/* you'll constantly bounce between the next two branches as the ring buffer is traversed. */
/* after N + 1 wraps */
if (tail_cpy > head_cpy) {
size_t space = tail_cpy - head_cpy - 1;
if (space >= requested_size) {
AWS_ATOMIC_STORE_HEAD_PTR(ring_buf, head_cpy + requested_size);
*dest = aws_byte_buf_from_empty_array(head_cpy, requested_size);
AWS_POSTCONDITION(aws_ring_buffer_is_valid(ring_buf));
AWS_POSTCONDITION(aws_byte_buf_is_valid(dest));
return AWS_OP_SUCCESS;
}
/* After N wraps */
} else if (tail_cpy < head_cpy) {
/* prefer the head space for efficiency. */
if ((size_t)(ring_buf->allocation_end - head_cpy) >= requested_size) {
AWS_ATOMIC_STORE_HEAD_PTR(ring_buf, head_cpy + requested_size);
*dest = aws_byte_buf_from_empty_array(head_cpy, requested_size);
AWS_POSTCONDITION(aws_ring_buffer_is_valid(ring_buf));
AWS_POSTCONDITION(aws_byte_buf_is_valid(dest));
return AWS_OP_SUCCESS;
}
if ((size_t)(tail_cpy - ring_buf->allocation) > requested_size) {
AWS_ATOMIC_STORE_HEAD_PTR(ring_buf, ring_buf->allocation + requested_size);
*dest = aws_byte_buf_from_empty_array(ring_buf->allocation, requested_size);
AWS_POSTCONDITION(aws_ring_buffer_is_valid(ring_buf));
AWS_POSTCONDITION(aws_byte_buf_is_valid(dest));
return AWS_OP_SUCCESS;
}
}
AWS_POSTCONDITION(aws_ring_buffer_is_valid(ring_buf));
AWS_POSTCONDITION(aws_byte_buf_is_valid(dest));
return aws_raise_error(AWS_ERROR_OOM);
}
int aws_ring_buffer_acquire_up_to(
struct aws_ring_buffer *ring_buf,
size_t minimum_size,
size_t requested_size,
struct aws_byte_buf *dest) {
AWS_PRECONDITION(requested_size >= minimum_size);
AWS_PRECONDITION(aws_ring_buffer_is_valid(ring_buf));
AWS_PRECONDITION(aws_byte_buf_is_valid(dest));
if (requested_size == 0 || minimum_size == 0 || !ring_buf || !dest) {
AWS_POSTCONDITION(aws_ring_buffer_is_valid(ring_buf));
AWS_POSTCONDITION(aws_byte_buf_is_valid(dest));
return aws_raise_error(AWS_ERROR_INVALID_ARGUMENT);
}
uint8_t *tail_cpy;
uint8_t *head_cpy;
AWS_ATOMIC_LOAD_TAIL_PTR(ring_buf, tail_cpy);
AWS_ATOMIC_LOAD_HEAD_PTR(ring_buf, head_cpy);
/* this branch is, we don't have any vended buffers. */
if (head_cpy == tail_cpy) {
size_t ring_space = ring_buf->allocation_end == NULL ? 0 : ring_buf->allocation_end - ring_buf->allocation;
size_t allocation_size = ring_space > requested_size ? requested_size : ring_space;
if (allocation_size < minimum_size) {
AWS_POSTCONDITION(aws_ring_buffer_is_valid(ring_buf));
AWS_POSTCONDITION(aws_byte_buf_is_valid(dest));
return aws_raise_error(AWS_ERROR_OOM);
}
/* go as big as we can. */
/* we don't have any vended, so this should be safe. */
AWS_ATOMIC_STORE_HEAD_PTR(ring_buf, ring_buf->allocation + allocation_size);
AWS_ATOMIC_STORE_TAIL_PTR(ring_buf, ring_buf->allocation);
*dest = aws_byte_buf_from_empty_array(ring_buf->allocation, allocation_size);
AWS_POSTCONDITION(aws_ring_buffer_is_valid(ring_buf));
AWS_POSTCONDITION(aws_byte_buf_is_valid(dest));
return AWS_OP_SUCCESS;
}
/* you'll constantly bounce between the next two branches as the ring buffer is traversed. */
/* after N + 1 wraps */
if (tail_cpy > head_cpy) {
size_t space = tail_cpy - head_cpy;
/* this shouldn't be possible. */
AWS_ASSERT(space);
space -= 1;
size_t returnable_size = space > requested_size ? requested_size : space;
if (returnable_size >= minimum_size) {
AWS_ATOMIC_STORE_HEAD_PTR(ring_buf, head_cpy + returnable_size);
*dest = aws_byte_buf_from_empty_array(head_cpy, returnable_size);
AWS_POSTCONDITION(aws_ring_buffer_is_valid(ring_buf));
AWS_POSTCONDITION(aws_byte_buf_is_valid(dest));
return AWS_OP_SUCCESS;
}
/* after N wraps */
} else if (tail_cpy < head_cpy) {
size_t head_space = ring_buf->allocation_end - head_cpy;
size_t tail_space = tail_cpy - ring_buf->allocation;
/* if you can vend the whole thing do it. Also prefer head space to tail space. */
if (head_space >= requested_size) {
AWS_ATOMIC_STORE_HEAD_PTR(ring_buf, head_cpy + requested_size);
*dest = aws_byte_buf_from_empty_array(head_cpy, requested_size);
AWS_POSTCONDITION(aws_ring_buffer_is_valid(ring_buf));
AWS_POSTCONDITION(aws_byte_buf_is_valid(dest));
return AWS_OP_SUCCESS;
}
if (tail_space > requested_size) {
AWS_ATOMIC_STORE_HEAD_PTR(ring_buf, ring_buf->allocation + requested_size);
*dest = aws_byte_buf_from_empty_array(ring_buf->allocation, requested_size);
AWS_POSTCONDITION(aws_ring_buffer_is_valid(ring_buf));
AWS_POSTCONDITION(aws_byte_buf_is_valid(dest));
return AWS_OP_SUCCESS;
}
/* now vend as much as possible, once again preferring head space. */
if (head_space >= minimum_size && head_space >= tail_space) {
AWS_ATOMIC_STORE_HEAD_PTR(ring_buf, head_cpy + head_space);
*dest = aws_byte_buf_from_empty_array(head_cpy, head_space);
AWS_POSTCONDITION(aws_ring_buffer_is_valid(ring_buf));
AWS_POSTCONDITION(aws_byte_buf_is_valid(dest));
return AWS_OP_SUCCESS;
}
if (tail_space > minimum_size) {
AWS_ATOMIC_STORE_HEAD_PTR(ring_buf, ring_buf->allocation + tail_space - 1);
*dest = aws_byte_buf_from_empty_array(ring_buf->allocation, tail_space - 1);
AWS_POSTCONDITION(aws_ring_buffer_is_valid(ring_buf));
AWS_POSTCONDITION(aws_byte_buf_is_valid(dest));
return AWS_OP_SUCCESS;
}
}
AWS_POSTCONDITION(aws_ring_buffer_is_valid(ring_buf));
AWS_POSTCONDITION(aws_byte_buf_is_valid(dest));
return aws_raise_error(AWS_ERROR_OOM);
}
static inline bool s_buf_belongs_to_pool(const struct aws_ring_buffer *ring_buffer, const struct aws_byte_buf *buf) {
#ifdef CBMC
/* only continue if buf points-into ring_buffer because comparison of pointers to different objects is undefined
* (C11 6.5.8) */
return (
__CPROVER_same_object(buf->buffer, ring_buffer->allocation) &&
AWS_IMPLIES(
ring_buffer->allocation_end != NULL, __CPROVER_same_object(buf->buffer, ring_buffer->allocation_end - 1)));
#endif
return buf->buffer && ring_buffer->allocation && ring_buffer->allocation_end &&
buf->buffer >= ring_buffer->allocation && buf->buffer + buf->capacity <= ring_buffer->allocation_end;
}
void aws_ring_buffer_release(struct aws_ring_buffer *ring_buffer, struct aws_byte_buf *buf) {
AWS_PRECONDITION(aws_ring_buffer_is_valid(ring_buffer));
AWS_PRECONDITION(aws_byte_buf_is_valid(buf));
AWS_PRECONDITION(s_buf_belongs_to_pool(ring_buffer, buf));
AWS_ATOMIC_STORE_TAIL_PTR(ring_buffer, buf->buffer + buf->capacity);
AWS_ZERO_STRUCT(*buf);
AWS_POSTCONDITION(aws_ring_buffer_is_valid(ring_buffer));
}
bool aws_ring_buffer_buf_belongs_to_pool(const struct aws_ring_buffer *ring_buffer, const struct aws_byte_buf *buf) {
AWS_PRECONDITION(aws_ring_buffer_is_valid(ring_buffer));
AWS_PRECONDITION(aws_byte_buf_is_valid(buf));
bool rval = s_buf_belongs_to_pool(ring_buffer, buf);
AWS_POSTCONDITION(aws_ring_buffer_is_valid(ring_buffer));
AWS_POSTCONDITION(aws_byte_buf_is_valid(buf));
return rval;
}
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