CLENQUEUEMAPBUFFER(3clc)

📦
version 1.0~svn33624 · 3 versions
, in ubuntu jammy, ubuntu noble

✨ NAME ✨

okay bestie, welcome to CLENQUEUEMAPBUFFER(3clc) from the OpenCL Manual 💖. This one is clEnqueueMapBuffer — it enqueues a command to map a region of the buffer object given by buffer into the host address space and returns a pointer to this mapped region. iconic, honestly.

void * clEnqueueMapBuffer(cl_command_queue command_queue, cl_mem buffer,
                          cl_bool blocking_map, cl_map_flags map_flags,
                          size_t offset, size_t size,
                          cl_uint num_events_in_wait_list,
                          const cl_event *event_wait_list,
                          cl_event *event, cl_int *errcode_ret);

🎀 PARAMETERS 🎀

  • command_queue — must be a valid command-queue. that's the vibe check, no exceptions 💅.
  • blocking_map — indicates if the map operation is blocking or non-blocking.

If blocking_map is CL_TRUE, clEnqueueMapBuffer does not return until the specified region in buffer is mapped into the host address space and the application can access the contents of the mapped region using the pointer returned by clEnqueueMapBuffer. 🫶

If blocking_map is CL_FALSE i.e. map operation is non-blocking, the pointer to the mapped region returned by clEnqueueMapBuffer cannot be used until the map command has completed. The event argument returns an event object which can be used to query the execution status of the map command. When the map command is completed, the application can access the contents of the mapped region using the pointer returned by clEnqueueMapBuffer. periodt.

  • map_flags — a bit-bield with the following supported cl_map_flags values. the tea:
    • CL_MAP_READ — this flag specifies that the region being mapped in the memory object is being mapped for reading. The pointer returned by clEnqueueMapBuffer or clEnqueueMapImage(3clc) is guaranteed to contain the latest bits in the region being mapped when the clEnqueueMapBuffer or clEnqueueMapImage(3clc) command has completed. ✨
    • CL_MAP_WRITE — this flag specifies that the region being mapped in the memory object is being mapped for writing. The pointer returned by clEnqueueMapBuffer or clEnqueueMapImage(3clc) is guaranteed to contain the latest bits in the region being mapped when the clEnqueueMapBuffer or clEnqueueMapImage(3clc) command has completed. 💖
    • CL_MAP_WRITE_INVALIDATE_REGION — this flag specifies that the region being mapped in the memory object is being mapped for writing. The contents of the region being mapped are to be discarded. This is typically the case when the region being mapped is overwritten by the host. This flag allows the implementation to no longer guarantee that the pointer returned by clEnqueueMapBuffer or clEnqueueMapImage(3clc) contains the latest bits in the region being mapped which can be a significant performance enhancement. CL_MAP_READ or CL_MAP_WRITE and CL_MAP_WRITE_INVALIDATE_REGION are mutually exclusive. 🚫
  • buffer — a valid buffer object. The OpenCL context associated with command_queue and buffer must be the same. iykyk.
  • offset, size — the offset in bytes and the size of the region in the buffer object that is being mapped. 📏
  • event_wait_list, num_events_in_wait_list — specify events that need to complete before this particular command can be executed. If event_wait_list is NULL, then this particular command does not wait on any event to complete. If event_wait_list is NULL, num_events_in_wait_list must be 0. If event_wait_list is not NULL, the list of events pointed to by event_wait_list must be valid and num_events_in_wait_list must be greater than 0. The events specified in event_wait_list act as synchronization points. The context associated with events in event_wait_list and command_queue must be the same. The memory associated with event_wait_list can be reused or freed after the function returns. slay.
  • event — returns an event object that identifies this particular copy command and can be used to query or queue a wait for this particular command to complete. event can be NULL in which case it will not be possible for the application to query the status of this command or queue a wait for this command to complete. If the event_wait_list and the event arguments are not NULL, the event argument should not refer to an element of the event_wait_list array. noted bestie.
  • errcode_ret — returns an appropriate error code. If errcode_ret is NULL, no error code is returned. 🫡

🌸 NOTES 🌸

The returned pointer maps a region starting at offset and is at least size bytes in size. The result of a memory access outside this region is undefined. do not do it, bestie 😭

If the buffer object is created with CL_MEM_USE_HOST_PTR set in mem_flags, the following will be true:

  • The host_ptr specified in clCreateBuffer(3clc) is guaranteed to contain the latest bits in the region being mapped when the clEnqueueMapBuffer command has completed. 💖
  • The pointer value returned by clEnqueueMapBuffer will be derived from the host_ptr specified when the buffer object is created. 🦋

Mapped buffer objects are unmapped using clEnqueueUnmapMemObject(3clc). 🔓

clEnqueueMapBuffer and clEnqueueMapImage(3clc) increment the mapped count of the memory object. The initial mapped count value of a memory object is zero. Multiple calls to clEnqueueMapBuffer or clEnqueueMapImage(3clc) on the same memory object will increment this mapped count by appropriate number of calls. clEnqueueUnmapMemObject(3clc) decrements the mapped count of the memory object. math is mathing.

clEnqueueMapBuffer and clEnqueueMapImage(3clc) act as synchronization points for a region of the buffer object being mapped. ✨ iconic behavior ✨

✨ ERRORS ✨

okay so bestie, if everything goes right, clEnqueueMapBuffer hands you back a pointer to the mapped region and sets errcode_ret to CL_SUCCESS. 💖

but if it's a no, you get a NULL pointer and errcode_ret gets one of these bad boys:

  • CL_INVALID_COMMAND_QUEUE — if command_queue is not a valid command-queue. 💀
  • CL_INVALID_CONTEXT — if the context associated with command_queue and image are not the same, or if the context associated with command_queue and events in event_wait_list are not the same. 🫠
  • CL_INVALID_MEM_OBJECT — if image is not a valid image object. 🙈
  • CL_INVALID_VALUE — if the region being mapped given by (offset, size) is out of bounds, or if size is 0, or if values specified in map_flags are not valid. 😭
  • CL_INVALID_EVENT_WAIT_LIST — if event_wait_list is NULL and num_events_in_wait_list > 0, or event_wait_list is not NULL and num_events_in_wait_list is 0, or if event objects in event_wait_list are not valid events. 🚩
  • CL_MISALIGNED_SUB_BUFFER_OFFSET — if buffer is a sub-buffer object and the offset specified when the sub-buffer object is created is not aligned to CL_DEVICE_MEM_BASE_ADDR_ALIGN value for the device associated with queue. 📐
  • CL_MAP_FAILURE — if there is a failure to map the requested region into the host address space. This error cannot occur for image objects created with CL_MEM_USE_HOST_PTR or CL_MEM_ALLOC_HOST_PTR. 💔
  • CL_EXEC_STATUS_ERROR_FOR_EVENTS_IN_WAIT_LIST — if the map operation is blocking and the execution status of any of the events in event_wait_list is a negative integer value. ⏳
  • CL_MEM_OBJECT_ALLOCATION_FAILURE — if there is a failure to allocate memory for data store associated with buffer. 🧠
  • CL_INVALID_OPERATION — if buffer has been created with CL_MEM_HOST_WRITE_ONLY or CL_MEM_HOST_NO_ACCESS and CL_MAP_READ is set in map_flags, or if buffer has been created with CL_MEM_HOST_READ_ONL or CL_MEM_HOST_NO_ACCESS and CL_MAP_WRITE or CL_MAP_WRITE_INVALIDATE_REGION is set in map_flags. 🚫
  • CL_OUT_OF_RESOURCES — if there is a failure to allocate resources required by the OpenCL implementation on the device. 🔋
  • CL_OUT_OF_HOST_MEMORY — if there is a failure to allocate resources required by the OpenCL implementation on the host. 🖥️

🌈 SPECIFICATION 🌈

OpenCL Specification[1]

🦋 SEE ALSO 🦋

👑 AUTHORS 👑

The Khronos Group

Copyright © 2007-2011 The Khronos Group Inc.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and/or associated documentation files (the "Materials"), to deal in the Materials without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Materials, and to permit persons to whom the Materials are furnished to do so, subject to the condition that this copyright notice and permission notice shall be included in all copies or substantial portions of the Materials.

🎀 NOTES 🎀

  1. OpenCL Specification page 86, section 5.2.3 - Mapping Buffer Objects
and that's the whole vibe, bestie! this iconic page comes from The Khronos Group, dated 01/14/2021, and the manpage is literally CLENQUEUEMAPBUFFER(3clc). stay mapping, slay, and always check your errcode_ret! 💅✨
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