buflib: Add buflib_context_relocate().
This function relocates a buflib back buffer, updating pointers in struct buflib_context. It does not move any data by itself. The intended use-case is buflib-on-buflib, where a buflib back buffer is allocated with buflib and attempted to be moved. The move_callback() can call this and return BUFLIB_CB_OK on success. No move_callback() is called for the subordinate buflib buffer, therefore it must not contain non-movable allocations. The caller is generally responsible moving the data and all its implications. Change-Id: I869219f9cff786a172c9e917a5f34470073892e6
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@ -117,6 +117,32 @@ buflib_init(struct buflib_context *ctx, void *buf, size_t size)
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(unsigned long)size / 1024, ((unsigned long)size%1000)/10);
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}
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bool buflib_context_relocate(struct buflib_context *ctx, void *buf)
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{
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union buflib_data *handle, *bd_buf = buf;
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ptrdiff_t diff = bd_buf - ctx->buf_start;
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/* cannot continue if the buffer is not aligned, since we would need
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* to reduce the size of the buffer for aligning */
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if ((uintptr_t)buf & 0x3)
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return false;
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/* relocate the handle table entries */
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for (handle = ctx->last_handle; handle < ctx->handle_table; handle++)
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{
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if (handle->alloc)
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handle->alloc += diff * sizeof(union buflib_data);
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}
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/* relocate the pointers in the context */
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ctx->handle_table += diff;
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ctx->last_handle += diff;
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ctx->first_free_handle += diff;
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ctx->buf_start += diff;
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ctx->alloc_end += diff;
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return true;
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}
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/* Allocate a new handle, returning 0 on failure */
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static inline
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union buflib_data* handle_alloc(struct buflib_context *ctx)
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@ -157,6 +157,21 @@ size_t buflib_available(struct buflib_context *ctx);
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*/
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size_t buflib_allocatable(struct buflib_context *ctx);
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/**
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* Relocates the fields in *ctx to the new buffer position pointed to by buf.
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* This does _not_ move any data but updates the pointers. The data has
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* to be moved afterwards manually and only if this function returned true.
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*
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* This is intended to be called from within a move_callback(), for
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* buflib-on-buflib scenarios (i.e. a new buflib instance backed by a buffer
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* that was allocated by another buflib instance). Be aware that if the parent
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* move_callback() moves the underlying buffer _no_ move_callback() of the
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* underlying buffer are called.
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*
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* Returns true of the relocation was successful. If it returns false no
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* change to *ctx was made.
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*/
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bool buflib_context_relocate(struct buflib_context *ctx, void *buf);
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/**
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* Allocates memory from buflib's memory pool
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