vl_stack.c File Reference

#include "vl_stack.h"
#include <memory.h>
#include <stdlib.h>

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Functions
void	vlStackInit (vl_stack *stack)
	Initializes the underlying memory of an existing vl_stack pointer. The stack allocator should be freed with vlStackFree.
void	vlStackFree (vl_stack *stack)
	Frees the specified stack instance's internal allocation.
vl_stack *	vlStackNew (void)
	Allocates on the heap, initializes, and returns a new stack allocator instance.
void	vlStackDelete (vl_stack *stack)
	Deletes the specified stack and its internal buffer.
void	vlStackReset (vl_stack *stack)
	Resets the specified stack allocator, allowing it to be used as if it had just been initialized.
vl_stack_offset	vlStackPush (vl_stack *stack, vl_memsize_t size)
	Reserves a new block of memory at the top of the stack, returning its offset.
vl_stack_offset	vlStackPushValue (vl_stack *stack, const void *data, vl_memsize_t size)
	Reserves and assigns a new block of memory at the top of the stack, returning its offset.
vl_transient *	vlStackSample (vl_stack *stack, vl_stack_offset offset)
	Samples the stack at the specified offset.
vl_memsize_t	vlStackSampleSize (vl_stack *stack, vl_stack_offset offset)
	Samples the size of the stack level at the specified offset.
vl_transient *	vlStackPeek (vl_stack *stack)
	Returns a pointer to the top level of the stack.
vl_memsize_t	vlStackPeekSize (vl_stack *stack)
	Returns the size of the top level of the stack, in bytes.
void	vlStackPop (vl_stack *stack)
	Pops the top level of the stack, allowing it to be overwritten in the future.

Function Documentation

vlStackDelete()

void vlStackDelete

(

vl_stack *

stack

)

Deletes the specified stack and its internal buffer.

This stack allocator should have been initialized via vlStackNew.

Contract

• Ownership: Releases ownership of the internal buffer and the vl_stack struct.
• Lifetime: The stack pointer and all its offsets become invalid.
• Thread Safety: Not thread-safe.
• Nullability: Safe to call if stack is NULL.
• Error Conditions: None.
• Undefined Behavior: Double deletion.
• Memory Allocation Expectations: Deallocates internal resources and the stack struct.
• Return-value Semantics: None (void).

See also

vlStackNew

Parameters

stack

pointer

Complexity of O(1) constant.

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vlStackFree()

void vlStackFree

(

vl_stack *

stack

)

Frees the specified stack instance's internal allocation.

Frees the internal buffer used by the stack allocator. This stack allocator should first be initialized via vlStackInit.

Contract

• Ownership: Releases ownership of the internal buffer. Does NOT release the stack struct itself.
• Lifetime: The stack becomes invalid for use.
• Thread Safety: Not thread-safe.
• Nullability: stack must not be NULL.
• Error Conditions: None.
• Undefined Behavior: Double free.
• Memory Allocation Expectations: Deallocates internal buffer data.
• Return-value Semantics: None (void).

See also

vlStackInit

Parameters

stack

pointer

Complexity of O(1) constant.

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vlStackInit()

void vlStackInit

(

vl_stack *

stack

)

Initializes the underlying memory of an existing vl_stack pointer. The stack allocator should be freed with vlStackFree.

Contract

• Ownership: The caller maintains ownership of the stack struct. The function initializes the internal buffer.
• Lifetime: The stack is valid until vlStackFree or vlStackDelete.
• Thread Safety: Not thread-safe.
• Nullability: stack must not be NULL.
• Error Conditions: None.
• Undefined Behavior: Passing an already initialized stack without first calling vlStackFree (causes memory leak).
• Memory Allocation Expectations: Initializes an internal vl_buffer which allocates an initial data block.
• Return-value Semantics: None (void).

Parameters

stack

stack pointer

See also

vlStackFree

Complexity of O(1) constant.

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vlStackNew()

vl_stack * vlStackNew

(

void

)

Allocates on the heap, initializes, and returns a new stack allocator instance.

Contract

• Ownership: The caller owns the returned vl_stack pointer and is responsible for calling vlStackDelete.
• Lifetime: The stack is valid until vlStackDelete.
• Thread Safety: Not thread-safe.
• Nullability: Returns NULL if heap allocation for the stack struct fails.
• Error Conditions: Returns NULL on allocation failure.
• Undefined Behavior: None.
• Memory Allocation Expectations: Allocates memory for the vl_stack struct and its internal buffer.
• Return-value Semantics: Returns a pointer to the newly allocated and initialized stack, or NULL.

See also

vlStackDelete

Complexity of O(1) constant.

Returns

stack allocator pointer located on the heap.

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vlStackPeek()

vl_transient * vlStackPeek

(

vl_stack *

stack

)

Returns a pointer to the top level of the stack.

Results in undefined behavior if the stack is empty.

Contract

• Ownership: Ownership remains with the stack.
• Lifetime: Valid until the next stack push, reset, or destruction.
• Thread Safety: Safe for concurrent reads if no thread is writing.
• Nullability: stack must not be NULL.
• Error Conditions: Undefined behavior if the stack is empty.
• Undefined Behavior: Peeking an empty stack.
• Memory Allocation Expectations: None.
• Return-value Semantics: Returns a transient pointer to the top data block.

Parameters

stack

pointer

Complexity of O(1) constant.

Returns

pointer to the top level of the stack.

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vlStackPeekSize()

vl_memsize_t vlStackPeekSize

(

vl_stack *

stack

)

Returns the size of the top level of the stack, in bytes.

Results in undefined behavior if the stack is empty.

Contract

• Ownership: None.
• Lifetime: Unchanged.
• Thread Safety: Safe for concurrent reads.
• Nullability: stack must not be NULL.
• Error Conditions: Undefined behavior if the stack is empty.
• Undefined Behavior: Peeking size of an empty stack.
• Memory Allocation Expectations: None.
• Return-value Semantics: Returns the size of the top element in bytes.

Parameters

stack

pointer

Complexity of O(1) constant.

Returns

size of the top level of the stack, in bytes.

vlStackPop()

void vlStackPop

(

vl_stack *

stack

)

Pops the top level of the stack, allowing it to be overwritten in the future.

Contract

• Ownership: Releases the top element's storage back to the stack.
• Lifetime: Sampled pointers to the popped element become invalid.
• Thread Safety: Not thread-safe.
• Nullability: stack must not be NULL.
• Error Conditions: None (no-op if the stack is empty).
• Undefined Behavior: Passing an uninitialized stack.
• Memory Allocation Expectations: None.
• Return-value Semantics: None (void).

Parameters

stack

Complexity of O(1) constant.

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vlStackPush()

vl_stack_offset vlStackPush	(	vl_stack *	stack,
		vl_memsize_t	size
	)

Reserves a new block of memory at the top of the stack, returning its offset.

This may force the underlying buffer to grow in size, which may invalidate the result of all prior calls to vlStackPeek and vlStackSample.

Contract

• Ownership: The stack maintains ownership of the memory. The caller receives an offset.
• Lifetime: The offset remains stable across buffer reallocations, but standard pointers derived from it are invalidated.
• Thread Safety: Not thread-safe.
• Nullability: stack must not be NULL.
• Error Conditions: Internal buffer expansion failure.
• Undefined Behavior: Passing an uninitialized stack.
• Memory Allocation Expectations: May trigger expansion of the underlying vl_buffer.
• Return-value Semantics: Returns the vl_stack_offset of the newly pushed block.

See also

vlStackPeek

vlStackPeekSize

vlStackSample

vlStackSampleSize

Parameters

stack	pointer
size	total bytes in the reserved block

Complexity of O(1) constant.

Returns

offset of the pushed stack level.

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vlStackPushValue()

vl_stack_offset vlStackPushValue	(	vl_stack *	stack,
		const void *	data,
		vl_memsize_t	size
	)

Reserves and assigns a new block of memory at the top of the stack, returning its offset.

This may force the underlying buffer to grow in size, which may invalidate the result of all prior calls to vlStackPeek and vlStackSample.

Contract

• Ownership: Unchanged. The stack maintains a copy of the provided data.
• Lifetime: Same as vlStackPush.
• Thread Safety: Not thread-safe.
• Nullability: stack must not be NULL. data should not be NULL.
• Error Conditions: Internal buffer expansion failure.
• Undefined Behavior: Passing an uninitialized stack.
• Memory Allocation Expectations: May trigger expansion of the underlying vl_buffer.
• Return-value Semantics: Returns the vl_stack_offset of the newly pushed block.

See also

vlStackPeek

vlStackPeekSize

vlStackSample

vlStackSampleSize

Parameters

stack	pointer
data	pointer to the element data
size	total bytes in the reserved block

Complexity of O(1) constant.

Returns

offset of the pushed stack level.

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vlStackReset()

void vlStackReset

(

vl_stack *

stack

)

Resets the specified stack allocator, allowing it to be used as if it had just been initialized.

This does NOT modify any of the information in the underlying buffer, but rather resets some variables used for book-keeping.

Contract

• Ownership: Unchanged.
• Lifetime: All previously returned offsets and sampled pointers become invalid.
• Thread Safety: Not thread-safe.
• Nullability: stack must not be NULL.
• Error Conditions: None.
• Undefined Behavior: Passing an uninitialized stack.
• Memory Allocation Expectations: None.
• Return-value Semantics: None (void).

Parameters

stack

pointer

Complexity of O(1) constant.

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vlStackSample()

vl_transient * vlStackSample	(	vl_stack *	stack,
		vl_stack_offset	offset
	)

Samples the stack at the specified offset.

Results in undefined behavior if the offset is invalid.

Contract

• Ownership: Ownership remains with the stack.
• Lifetime: Valid until the next operation that may reallocate the underlying buffer.
• Thread Safety: Safe for concurrent reads.
• Nullability: stack must not be NULL.
• Error Conditions: Undefined behavior if the offset is invalid.
• Undefined Behavior: Passing an invalid offset.
• Memory Allocation Expectations: None.
• Return-value Semantics: Returns a transient pointer to the memory at the specified offset.

Parameters

stack	pointer
offset	level of the stack to sample

Complexity of O(1) constant.

Returns

pointer to memory managed by the stack allocator.

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vlStackSampleSize()

vl_memsize_t vlStackSampleSize	(	vl_stack *	stack,
		vl_stack_offset	offset
	)

Samples the size of the stack level at the specified offset.

Results in undefined behavior if the specified offset is invalid.

Contract

• Ownership: None.
• Lifetime: Unchanged.
• Thread Safety: Safe for concurrent reads.
• Nullability: stack must not be NULL.
• Error Conditions: Undefined behavior if the offset is invalid.
• Undefined Behavior: Passing an invalid offset.
• Memory Allocation Expectations: None.
• Return-value Semantics: Returns the size of the stack level in bytes.

Parameters

stack	pointer
offset	level of the stack

Complexity of O(1) constant.

Returns

size of the specified level of the stack, in bytes.