PART 9: Dynamic memory allocation

null=0 ≤ MEM_MIN=0 ≤ MEM_BOT=0 < lo_mem_max < hi_mem_min < MEM_TOP=3_000_000 ≤ mem_end ≤ MEM_MAX=3_000_000 . 更多...

宏定义
#define	null   0
	[p44#115] the null pointer. 更多...
#define	link(x)   (mem[(x)].hh.rh)
	[p45#118] the link field of a memory word. 更多...
#define	info(x)   (mem[(x)].hh.UU.lh)
	[p45#118] the info field of a memory word. 更多...
#define	empty_flag   MAX_HALF_WORD
	[p46#124] the link of an empty variable-size node. 更多...
#define	is_empty(x)   (link(x) == empty_flag)
	[p46#124] tests for empty node. 更多...
#define	node_size   info
	[p46#124] the size field in empty variable-size nodes. 更多...
#define	llink(x)   info(x+1)
	[p46#124] left link in doubly-linked list of empty nodes. 更多...
#define	rlink(x)   link(x+1)
	[p46#124] right link in doubly-linked list of empty nodes. 更多...
#define	FREE_AVAIL(x)   (link(x) = avail, avail = (x), dyn_used -= CHAR_NODE_SIZE)
	[p45#121] single-word node liberation. 更多...
#define	FAST_GET_AVAIL(x)
	[#122] avoid get_avail() if possible, to save time. 更多...

函数
Pointer	get_lo_mem_max (void)
Pointer	get_avail (void)
	[p45#120]: single-word node allocation. 更多...
void	flush_list (HalfWord p)
	[p46#123]: makes list of single-word nodes available 更多...
HalfWord	get_node (Integer s)
	[p47#125] variable-size node allocation 更多...
void	free_node (Pointer p, HalfWord s)
	[p48#130]: variable-size node liberation 更多...
void	sort_avail (void)
	p49#131: sorts the available variable-size nodes by location used at #1311 更多...

变量
Pointer	temp_ptr
	[#115] for occasional emergency use. 更多...
MemoryWord	mem [MEM_MAX - MEM_MIN+1]
	[#116] the big dynamic storage area. 更多...
Pointer	lo_mem_max
	[#116] the largest location of variable-size memory. 更多...
Pointer	hi_mem_min
	[#116] the smallest location of one-word memory. 更多...
Integer	var_used
Integer	dyn_used
	[#117] how much memory is in use. 更多...
Pointer	avail
	[#118] head of the list of available one-word nodes. 更多...
Pointer	mem_end
	[#118] the last one-word node used in mem. 更多...
Pointer	rover
	[#124] points to some node in the list of empties. 更多...

详细描述

null=0 ≤ MEM_MIN=0 ≤ MEM_BOT=0 < lo_mem_max < hi_mem_min < MEM_TOP=3_000_000 ≤ mem_end ≤ MEM_MAX=3_000_000 .

宏定义说明

empty_flag

#define empty_flag   MAX_HALF_WORD

[p46#124] the link of an empty variable-size node.

FAST_GET_AVAIL

#define FAST_GET_AVAIL

(

x

)

值:

    do {                                \
        if (((x) = avail) != null) {    \
            type(x) = charnodetype;     \
            avail = link(x);            \
            link(x) = null;             \
            dyn_used += CHAR_NODE_SIZE; \
        } else {                        \
            (x) = get_avail();          \
        }                               \
    } while (0)

[#122] avoid get_avail() if possible, to save time.

FREE_AVAIL

#define FREE_AVAIL

(

x

)

(link(x) = avail, avail = (x), dyn_used -= CHAR_NODE_SIZE)

[p45#121] single-word node liberation.

a one-word node is recycled by calling FREE_AVAIL.

info

#define info

(

x

)

(mem[(x)].hh.UU.lh)

[p45#118] the info field of a memory word.

is_empty

#define is_empty

(

x

)

(link(x) == empty_flag)

[p46#124] tests for empty node.

link

#define link

(

x

)

(mem[(x)].hh.rh)

[p45#118] the link field of a memory word.

llink

#define llink

(

x

)

info(x+1)

[p46#124] left link in doubly-linked list of empty nodes.

node_size

#define node_size   info

[p46#124] the size field in empty variable-size nodes.

null

#define null   0

[p44#115] the null pointer.

null ≡ min_halfword.

rlink

#define rlink

(

x

)

link(x+1)

[p46#124] right link in doubly-linked list of empty nodes.

函数说明

flush_list()

void flush_list

(

HalfWord

p

)

[p46#123]: makes list of single-word nodes available

free_node()

void free_node	(	Pointer	p,
		HalfWord	s
	)

[p48#130]: variable-size node liberation

get_avail()

Pointer get_avail

(

void

)

[p45#120]: single-word node allocation.

get_lo_mem_max()

Pointer get_lo_mem_max

(

void

)

get_node()

HalfWord get_node

(

Integer

s

)

[p47#125] variable-size node allocation

[#127] Try to allocate within node p and its physical successors, and goto found if allocation was possible.

[#126] Grow more variable-size memory and goto restart

sort_avail()

void sort_avail

(

void

)

p49#131: sorts the available variable-size nodes by location used at #1311

#132: Sort p into the list starting at rover and ADVANCE p to rlink(p)

变量说明

avail

Pointer avail

[#118] head of the list of available one-word nodes.

dyn_used

Integer dyn_used

[#117] how much memory is in use.

hi_mem_min

Pointer hi_mem_min

[#116] the smallest location of one-word memory.

lo_mem_max

Pointer lo_mem_max

[#116] the largest location of variable-size memory.

mem

MemoryWord mem[MEM_MAX - MEM_MIN+1]

[#116] the big dynamic storage area.

mem_end

Pointer mem_end

[#118] the last one-word node used in mem.

rover

Pointer rover

[#124] points to some node in the list of empties.

temp_ptr

Pointer temp_ptr

[#115] for occasional emergency use.

var_used

Integer var_used