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The slab initialization code includes the calculation of the slab 'elem_size', which is in turn used to determine the size (capacity) of the slab. Each element of the slab represents an array, of length 'stride', of 'elemtype'. (Note that it may be clearer if the define_commit_slab macro parameter was called 'basetype' rather than 'elemtype'). However, the 'elem_size' calculation incorrectly uses 'sizeof(struct slabname)' in the expression, rather than 'sizeof(elemtype)'. Within the slab access routine, <slabname>_at(), the given commit 'index' is transformed into an (slab#, slot#) pair used to address the required element (a pointer to the first element of the array of 'elemtype' associated with that commit). The current code to calculate these address coordinates multiplies the commit index by the 'stride' which, at least for the slab#, produces the wrong result. Using the commit index directly, without scaling by the 'stride', produces the correct 'logical' address. Also, when allocating a new slab, the size of the allocation only allows for a slab containing elements of single element arrays of 'elemtype'. This should allow for elements of an array of length 'stride' of 'elemtype'. In order to fix this, we need to change the element size parameter to xcalloc() by multiplying the current element size (sizeof(**s->slab)) by the s->stride. Having changed the calculation of the slot#, we now need to convert the logical 'nth_slot', by scaling with s->stride, into the correct physical address. Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk> Signed-off-by: Junio C Hamano <gitster@pobox.com>
98 lines
2.9 KiB
C
98 lines
2.9 KiB
C
#ifndef COMMIT_SLAB_H
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#define COMMIT_SLAB_H
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/*
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* define_commit_slab(slabname, elemtype) creates boilerplate code to define
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* a new struct (struct slabname) that is used to associate a piece of data
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* of elemtype to commits, and a few functions to use that struct.
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*
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* After including this header file, using:
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*
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* define_commit_slab(indegee, int);
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*
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* will let you call the following functions:
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*
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* - int *indegree_at(struct indegree *, struct commit *);
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*
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* This function locates the data associated with the given commit in
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* the indegree slab, and returns the pointer to it.
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*
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* - void init_indegree(struct indegree *);
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* void init_indegree_with_stride(struct indegree *, int);
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*
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* Initializes the indegree slab that associates an array of integers
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* to each commit. 'stride' specifies how big each array is. The slab
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* that id initialied by the variant without "_with_stride" associates
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* each commit with an array of one integer.
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*/
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/* allocate ~512kB at once, allowing for malloc overhead */
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#ifndef COMMIT_SLAB_SIZE
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#define COMMIT_SLAB_SIZE (512*1024-32)
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#endif
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#define define_commit_slab(slabname, elemtype) \
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\
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struct slabname { \
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unsigned slab_size; \
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unsigned stride; \
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unsigned slab_count; \
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elemtype **slab; \
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}; \
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static int stat_ ##slabname## realloc; \
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\
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static void init_ ##slabname## _with_stride(struct slabname *s, \
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unsigned stride) \
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{ \
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unsigned int elem_size; \
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if (!stride) \
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stride = 1; \
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s->stride = stride; \
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elem_size = sizeof(elemtype) * stride; \
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s->slab_size = COMMIT_SLAB_SIZE / elem_size; \
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s->slab_count = 0; \
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s->slab = NULL; \
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} \
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\
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static void init_ ##slabname(struct slabname *s) \
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{ \
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init_ ##slabname## _with_stride(s, 1); \
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} \
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\
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static void clear_ ##slabname(struct slabname *s) \
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{ \
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int i; \
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for (i = 0; i < s->slab_count; i++) \
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free(s->slab[i]); \
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s->slab_count = 0; \
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free(s->slab); \
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s->slab = NULL; \
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} \
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\
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static elemtype *slabname## _at(struct slabname *s, \
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const struct commit *c) \
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{ \
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int nth_slab, nth_slot; \
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\
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nth_slab = c->index / s->slab_size; \
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nth_slot = c->index % s->slab_size; \
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\
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if (s->slab_count <= nth_slab) { \
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int i; \
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s->slab = xrealloc(s->slab, \
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(nth_slab + 1) * sizeof(s->slab)); \
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stat_ ##slabname## realloc++; \
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for (i = s->slab_count; i <= nth_slab; i++) \
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s->slab[i] = NULL; \
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s->slab_count = nth_slab + 1; \
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} \
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if (!s->slab[nth_slab]) \
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s->slab[nth_slab] = xcalloc(s->slab_size, \
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sizeof(**s->slab) * s->stride); \
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return &s->slab[nth_slab][nth_slot * s->stride]; \
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} \
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\
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static int stat_ ##slabname## realloc
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#endif /* COMMIT_SLAB_H */
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