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The C Users' Group Library 1994 August
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wc-cdrom-cusersgrouplibrary-1994-08.iso
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vol_300
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318_01
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redbuf.h
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1990-06-18
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/*
Header for global buffer constants, structures.
Source: redbuf.h
Version: November 15, 1983; January 18, 1990.
Written by
Edward K. Ream
166 N. Prospect
Madison WI 53705
(608) 257-0802
PUBLIC DOMAIN SOFTWARE
This software is in the public domain.
See red.h for a disclaimer of warranties and other information.
*/
/*
You may tune these constants for better disk performance.
DATA_SIZE: The size of that part of struct BLOCK which is
written to the disk. Make sure that DATA_SIZE
is a multiple of the size of your disk sectors.
MAX_RES: The maximum number of BLOCKS resident in memory.
The code assumes this number is at least MIN_RES.
The actual number of resident blocks is DATA_RES.
DATA_RES is set by calling alloc(DATA_SIZE) until
MAX_RES blocks are allocated or until alloc() fails.
I recommend MAX_RES = 40 so that the small data model
can be used.
*/
#define DATA_SIZE 1024
#define MAX_RES 40 /* must have MIN_RES <= MAX_RES */
/*
!! Do NOT change the following constant !!
The MIN_RES constant determines the minimum number of blocks that
must be allocated for RED to work properly. MIN_RES must be large
enough so that the combine routine will work properly. Determining
the true lower bound is tricky, and 10 is sure to work.
*/
#define MIN_RES 10
#if MAX_RES < MIN_RES
#error too few buffers specified.
#endif
/*
Partially define the format of a block. The end of
the data area contains an "index table" of indices
into the front of the data area. Each index is the
index of the last byte of a line.
Thus, it is possible to calculate the starting address
and length of each line in the block WITHOUT searching
through either the data field or the index table.
The d_back and d_next fields in the header are used
to doubly-link the disk blocks so that stepping
through the blocks either forward or backwards is
efficient. -1 denotes the end of each list.
When blocks become totally empty they are entered
on a list of free blocks. The links of this list
are kept in the blocks themselves in the d_next field.
The b_free variable is the head of this list.
*/
/*
Warning!! RED will crash if the following two
defines are not right.
*/
#define HEADER_SIZE 3*sizeof(int) /* size of the block header */
#define STATUS_SIZE 3*sizeof(int) /* size of the status table */
#define BUFF_SIZE (DATA_SIZE - HEADER_SIZE)
#define BLOCK_SIZE (DATA_SIZE + STATUS_SIZE)
struct BLOCK {
/* The block header. */
int d_back; /* # of previous block */
int d_next; /* # of next block */
int d_lines; /* # of lines on block */
/* The data area and index table. */
char d_data [BUFF_SIZE];
/* The status table -- not written to disk. */
int d_lru; /* lru count */
int d_status; /* FULL, FREE or DIRTY */
int d_diskp; /* disk pointer */
};
/*
Define the entries in the d_status field.
*/
#define FREE 1 /* status: block is available */
#define FULL 2 /* status: block is allocated */
#define DIRTY 3 /* status: must swap out */
#define bufatbot() (b_line > b_max_line)
#define bufattop() (b_line == 1)
#define bufchng() b_cflag
#define bufln() b_line
#define bufmax() b_max_line
#define bufnrbot() (b_line >= b_max_line)
/*
The following are all defined as macros for much greater speed.
These macros replace corresponding functions in redbuf2.c.
See those functions for an explanation of what these macros do.
*/
#define b1_avail() b_avail(b_bp)
#define b1_length(line) b_length(b_bp, (line))
#define b1_nlines() (b_bp -> d_lines)
#define b1_prefix(line) b_prefix(b_bp, (line))
#define b1_ptr(line) b_ptr(b_bp, (line))
#define b1_settab(index, value) b_settab(b_bp, (index), (value))
#define b1_tab(index) b_tab(b_bp, (index))
#define b_getnum(p) (* ((int *) (p)))
#define b_putnum(p, num) (* ((int *) (p)) = (num))
#define b_avail(bp) \
( ((bp)-> d_lines==0) ? BUFF_SIZE : \
(BUFF_SIZE-b_tab((bp),(bp)->d_lines-1)-(sizeof(int)*bp->d_lines)) )
#define b_length(bp,line) \
( (bufatbot()) ? 0 : \
( ((line)==0) ? (b_tab((bp), line)) : \
(b_tab((bp),(line)) - b_tab((bp),(line)-1)) ))
#define b_nlines(bp) ((bp) -> d_lines)
#define b_prefix(bp, line) \
( ((line)==0) ? 0 : (b_tab((bp),(line)-1)) )
#define b_ptr(bp, line) \
( ((line)==0) ? ((bp)->d_data) : \
((bp)->d_data + b_tab((bp),(line)-1)) )
#define b_settab(bp,index,value) \
b_putnum((bp)->d_data+BUFF_SIZE-(sizeof(int)*((index)+1)),(value))
#define b_tab(bp, index) \
b_getnum((bp)->d_data+BUFF_SIZE-(sizeof(int)*((index)+1)))
#define is_dirty(bp) ((bp) -> d_status = DIRTY)