|
|
/* Copyright (C) 2001-2017 Peter Selinger.
* This file is part of Potrace. It is free software and it is covered * by the GNU General Public License. See the file COPYING for details. */
#ifndef _PS_LISTS_H
#define _PS_LISTS_H
/* here we define some general list macros. Because they are macros,
* they should work on any datatype with a "->next" component. Some of * them use a "hook". If elt and list are of type t* then hook is of * type t**. A hook stands for an insertion point in the list, i.e., * either before the first element, or between two elements, or after * the last element. If an operation "sets the hook" for an element, * then the hook is set to just before the element. One can insert * something at a hook. One can also unlink at a hook: this means, * unlink the element just after the hook. By "to unlink", we mean the * element is removed from the list, but not deleted. Thus, it and its * components still need to be freed. */
/* Note: these macros are somewhat experimental. Only the ones that
* are actually *used* have been tested. So be careful to test any * that you use. Looking at the output of the preprocessor, "gcc -E" * (possibly piped though "indent"), might help too. Also: these * macros define some internal (local) variables that start with * "_". */
/* we enclose macro definitions whose body consists of more than one
* statement in MACRO_BEGIN and MACRO_END, rather than '{' and '}'. The * reason is that we want to be able to use the macro in a context * such as "if (...) macro(...); else ...". If we didn't use this obscure * trick, we'd have to omit the ";" in such cases. */
#define MACRO_BEGIN \
do \ {#define MACRO_END \
} \ while( 0 )
/* ---------------------------------------------------------------------- *//* macros for singly-linked lists */
/* traverse list. At the end, elt is set to NULL. */#define list_forall( elt, list ) for( elt = list; elt != NULL; elt = elt->next )
/* set elt to the first element of list satisfying boolean condition
* c, or NULL if not found */#define list_find( elt, list, c ) \
MACRO_BEGIN list_forall( elt, list ) if( c ) \ break; \ MACRO_END
/* like forall, except also set hook for elt. */#define list_forall2( elt, list, hook ) \
for( elt = list, hook = &list; elt != NULL; hook = &elt->next, elt = elt->next )
/* same as list_find, except also set hook for elt. */#define list_find2( elt, list, c, hook ) \
MACRO_BEGIN list_forall2( elt, list, hook ) if( c ) \ break; \ MACRO_END
/* same, except only use hook. */#define _list_forall_hook( list, hook ) for( hook = &list; *hook != NULL; hook = &( *hook )->next )
/* same, except only use hook. Note: c may only refer to *hook, not elt. */#define _list_find_hook( list, c, hook ) \
MACRO_BEGIN _list_forall_hook( list, hook ) if( c ) \ break; \ MACRO_END
/* insert element after hook */#define list_insert_athook( elt, hook ) \
MACRO_BEGIN elt->next = *hook; \ *hook = elt; \ MACRO_END
/* insert element before hook */#define list_insert_beforehook( elt, hook ) \
MACRO_BEGIN elt->next = *hook; \ *hook = elt; \ hook = &elt->next; \ MACRO_END
/* unlink element after hook, let elt be unlinked element, or NULL.
* hook remains. */#define list_unlink_athook( list, elt, hook ) \
MACRO_BEGIN \ elt = hook ? *hook : NULL; \ if( elt ) \ { \ *hook = elt->next; \ elt->next = NULL; \ } \ MACRO_END
/* unlink the specific element, if it is in the list. Otherwise, set
* elt to NULL */#define list_unlink( listtype, list, elt ) \
MACRO_BEGIN \ listtype * *_hook; \ _list_find_hook( list, *_hook == elt, _hook ); \ list_unlink_athook( list, elt, _hook ); \ MACRO_END
/* prepend elt to list */#define list_prepend( list, elt ) \
MACRO_BEGIN elt->next = list; \ list = elt; \ MACRO_END
/* append elt to list. */#define list_append( listtype, list, elt ) \
MACRO_BEGIN \ listtype * *_hook; \ _list_forall_hook( list, _hook ) \ { \ } \ list_insert_athook( elt, _hook ); \ MACRO_END
/* unlink the first element that satisfies the condition. */#define list_unlink_cond( listtype, list, elt, c ) \
MACRO_BEGIN \ listtype * *_hook; \ list_find2( elt, list, c, _hook ); \ list_unlink_athook( list, elt, _hook ); \ MACRO_END
/* let elt be the nth element of the list, starting to count from 0.
* Return NULL if out of bounds. */#define list_nth( elt, list, n ) \
MACRO_BEGIN \ int _x; /* only evaluate n once */ \ for( _x = ( n ), elt = list; _x && elt; _x--, elt = elt->next ) \ { \ } \ MACRO_END
/* let elt be the nth element of the list, starting to count from 0.
* Return NULL if out of bounds. */#define list_nth_hook( elt, list, n, hook ) \
MACRO_BEGIN \ int _x; /* only evaluate n once */ \ for( _x = ( n ), elt = list, hook = &list; _x && elt; \ _x--, hook = &elt->next, elt = elt->next ) \ { \ } \ MACRO_END
/* set n to the length of the list */#define list_length( listtype, list, n ) \
MACRO_BEGIN \ listtype * _elt; \ n = 0; \ list_forall( _elt, list ) n++; \ MACRO_END
/* set n to the index of the first element satisfying cond, or -1 if
* none found. Also set elt to the element, or NULL if none found. */#define list_index( list, n, elt, c ) \
MACRO_BEGIN \ n = 0; \ list_forall( elt, list ) \ { \ if( c ) \ break; \ n++; \ } \ if( !elt ) \ n = -1; \ MACRO_END
/* set n to the number of elements in the list that satisfy condition c */#define list_count( list, n, elt, c ) \
MACRO_BEGIN \ n = 0; \ list_forall( elt, list ) \ { \ if( c ) \ n++; \ } \ MACRO_END
/* let elt be each element of the list, unlinked. At the end, set list=NULL. */#define list_forall_unlink( elt, list ) \
for( elt = list; elt ? ( list = elt->next, elt->next = NULL ), 1 : 0; elt = list )
/* reverse a list (efficient) */#define list_reverse( listtype, list ) \
MACRO_BEGIN \ listtype * _list1 = NULL, *elt; \ list_forall_unlink( elt, list ) list_prepend( _list1, elt ); \ list = _list1; \ MACRO_END
/* insert the element ELT just before the first element TMP of the
* list for which COND holds. Here COND must be a condition of ELT and * TMP. Typical usage is to insert an element into an ordered list: * for instance, list_insert_ordered(listtype, list, elt, tmp, * elt->size <= tmp->size). Note: if we give a "less than or equal" * condition, the new element will be inserted just before a sequence * of equal elements. If we give a "less than" condition, the new * element will be inserted just after a list of equal elements. * Note: it is much more efficient to construct a list with * list_prepend and then order it with list_merge_sort, than to * construct it with list_insert_ordered. */#define list_insert_ordered( listtype, list, elt, tmp, cond ) \
MACRO_BEGIN \ listtype * *_hook; \ _list_find_hook( list, ( tmp = *_hook, ( cond ) ), _hook ); \ list_insert_athook( elt, _hook ); \ MACRO_END
/* sort the given list, according to the comparison condition.
* Typical usage is list_sort(listtype, list, a, b, a->size < * b->size). Note: if we give "less than or equal" condition, each * segment of equal elements will be reversed in order. If we give a * "less than" condition, each segment of equal elements will retain * the original order. The latter is slower but sometimes * prettier. Average running time: n*n/2. */#define list_sort( listtype, list, a, b, cond ) \
MACRO_BEGIN \ listtype * _newlist = NULL; \ list_forall_unlink( a, list ) list_insert_ordered( listtype, _newlist, a, b, cond ); \ list = _newlist; \ MACRO_END
/* a much faster sort algorithm (merge sort, n log n worst case). It
* is required that the list type has an additional, unused next1 * component. Note there is no curious reversal of order of equal * elements as for list_sort. */
#define list_mergesort( listtype, list, a, b, cond ) \
MACRO_BEGIN \ listtype * _elt, **_hook1; \ \ for( _elt = list; _elt; _elt = _elt->next1 ) \ { \ _elt->next1 = _elt->next; \ _elt->next = NULL; \ } \ do \ { \ _hook1 = &( list ); \ while( ( a = *_hook1 ) != NULL && ( b = a->next1 ) != NULL ) \ { \ _elt = b->next1; \ _list_merge_cond( listtype, a, b, cond, *_hook1 ); \ _hook1 = &( ( *_hook1 )->next1 ); \ *_hook1 = _elt; \ } \ } \ while( _hook1 != &( list ) ); \ MACRO_END
/* merge two sorted lists. Store result at &result */#define _list_merge_cond( listtype, a, b, cond, result ) \
MACRO_BEGIN \ listtype * *_hook; \ _hook = &( result ); \ while( 1 ) \ { \ if( a == NULL ) \ { \ *_hook = b; \ break; \ } \ else if( b == NULL ) \ { \ *_hook = a; \ break; \ } \ else if( cond ) \ { \ *_hook = a; \ _hook = &( a->next ); \ a = a->next; \ } \ else \ { \ *_hook = b; \ _hook = &( b->next ); \ b = b->next; \ } \ } \ MACRO_END
/* ---------------------------------------------------------------------- *//* macros for doubly-linked lists */
#define dlist_append( head, end, elt ) \
MACRO_BEGIN \ elt->prev = end; \ elt->next = NULL; \ if( end ) \ { \ end->next = elt; \ } \ else \ { \ head = elt; \ } \ end = elt; \ MACRO_END
/* let elt be each element of the list, unlinked. At the end, set list=NULL. */#define dlist_forall_unlink( elt, head, end ) \
for( elt = head; \ elt ? ( head = elt->next, elt->next = NULL, elt->prev = NULL ), 1 : ( end = NULL, 0 ); \ elt = head )
/* unlink the first element of the list */#define dlist_unlink_first( head, end, elt ) \
MACRO_BEGIN \ elt = head; \ if( head ) \ { \ head = head->next; \ if( head ) \ { \ head->prev = NULL; \ } \ else \ { \ end = NULL; \ } \ elt->prev = NULL; \ elt->next = NULL; \ } \ MACRO_END
#endif /* _PS_LISTS_H */
|
