| 1 | @node Obstacks,Licenses,Functions,Top
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| 2 | @chapter Obstacks
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| 3 | @cindex obstacks
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| 4 |
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| 5 | An @dfn{obstack} is a pool of memory containing a stack of objects. You
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| 6 | can create any number of separate obstacks, and then allocate objects in
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| 7 | specified obstacks. Within each obstack, the last object allocated must
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| 8 | always be the first one freed, but distinct obstacks are independent of
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| 9 | each other.
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| 10 |
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| 11 | Aside from this one constraint of order of freeing, obstacks are totally
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| 12 | general: an obstack can contain any number of objects of any size. They
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| 13 | are implemented with macros, so allocation is usually very fast as long as
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| 14 | the objects are usually small. And the only space overhead per object is
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| 15 | the padding needed to start each object on a suitable boundary.
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| 16 |
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| 17 | @menu
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| 18 | * Creating Obstacks:: How to declare an obstack in your program.
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| 19 | * Preparing for Obstacks:: Preparations needed before you can
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| 20 | use obstacks.
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| 21 | * Allocation in an Obstack:: Allocating objects in an obstack.
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| 22 | * Freeing Obstack Objects:: Freeing objects in an obstack.
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| 23 | * Obstack Functions:: The obstack functions are both
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| 24 | functions and macros.
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| 25 | * Growing Objects:: Making an object bigger by stages.
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| 26 | * Extra Fast Growing:: Extra-high-efficiency (though more
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| 27 | complicated) growing objects.
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| 28 | * Status of an Obstack:: Inquiries about the status of an obstack.
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| 29 | * Obstacks Data Alignment:: Controlling alignment of objects in obstacks.
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| 30 | * Obstack Chunks:: How obstacks obtain and release chunks;
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| 31 | efficiency considerations.
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| 32 | * Summary of Obstacks::
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| 33 | @end menu
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| 34 |
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| 35 | @node Creating Obstacks
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| 36 | @section Creating Obstacks
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| 37 |
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| 38 | The utilities for manipulating obstacks are declared in the header
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| 39 | file @file{obstack.h}.
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| 40 | @pindex obstack.h
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| 41 |
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| 42 | @comment obstack.h
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| 43 | @comment GNU
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| 44 | @deftp {Data Type} {struct obstack}
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| 45 | An obstack is represented by a data structure of type @code{struct
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| 46 | obstack}. This structure has a small fixed size; it records the status
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| 47 | of the obstack and how to find the space in which objects are allocated.
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| 48 | It does not contain any of the objects themselves. You should not try
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| 49 | to access the contents of the structure directly; use only the functions
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