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Use backtick code blocks for syntax highlighting

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James Gregory 2013-12-31 11:38:48 +11:00
commit f658bfbb40
203 changed files with 26546 additions and 25801 deletions
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194
01-05.md
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@ -30,62 +30,64 @@ uses no assembly at all.
**LISTING 1.5 L1-5.C**
/*
* Program to calculate the 16-bit checksum of the stream of bytes
* from the specified file. Buffers the bytes internally, rather
* than letting C or DOS do the work.
*/
#include <stdio.h>
#include <fcntl.h>
#include <alloc.h> /* alloc.h for Borland,
malloc.h for Microsoft */
```c
/*
* Program to calculate the 16-bit checksum of the stream of bytes
* from the specified file. Buffers the bytes internally, rather
* than letting C or DOS do the work.
*/
#include <stdio.h>
#include <fcntl.h>
#include <alloc.h> /* alloc.h for Borland,
malloc.h for Microsoft */
#define BUFFER_SIZE 0x8000 /* 32Kb data buffer */
#define BUFFER_SIZE 0x8000 /* 32Kb data buffer */
main(int argc, char *argv[]) {
int Handle;
unsigned int Checksum;
unsigned char *WorkingBuffer, *WorkingPtr;
int WorkingLength, LengthCount;
main(int argc, char *argv[]) {
int Handle;
unsigned int Checksum;
unsigned char *WorkingBuffer, *WorkingPtr;
int WorkingLength, LengthCount;
if ( argc != 2 ) {
printf("usage: checksum filename\n");
exit(1);
}
if ( (Handle = open(argv[1], O_RDONLY | O_BINARY)) == -1 ) {
printf("Can't open file: %s\n", argv[1]);
exit(1);
}
if ( argc != 2 ) {
printf("usage: checksum filename\n");
exit(1);
}
if ( (Handle = open(argv[1], O_RDONLY | O_BINARY)) == -1 ) {
printf("Can't open file: %s\n", argv[1]);
exit(1);
}
/* Get memory in which to buffer the data */
if ( (WorkingBuffer = malloc(BUFFER_SIZE)) == NULL ) {
printf("Can't get enough memory\n");
exit(1);
}
/* Get memory in which to buffer the data */
if ( (WorkingBuffer = malloc(BUFFER_SIZE)) == NULL ) {
printf("Can't get enough memory\n");
exit(1);
}
/* Initialize the checksum accumulator */
Checksum = 0;
/* Initialize the checksum accumulator */
Checksum = 0;
/* Process the file in BUFFER_SIZE chunks */
do {
if ( (WorkingLength = read(Handle, WorkingBuffer,
BUFFER_SIZE)) == -1 ) {
printf("Error reading file %s\n", argv[1]);
exit(1);
}
/* Checksum this chunk */
WorkingPtr = WorkingBuffer;
LengthCount = WorkingLength;
while ( LengthCount-- ) {
/* Add each byte in turn into the checksum accumulator */
Checksum += (unsigned int) *WorkingPtr++;
}
} while ( WorkingLength );
/* Process the file in BUFFER_SIZE chunks */
do {
if ( (WorkingLength = read(Handle, WorkingBuffer,
BUFFER_SIZE)) == -1 ) {
printf("Error reading file %s\n", argv[1]);
exit(1);
}
/* Checksum this chunk */
WorkingPtr = WorkingBuffer;
LengthCount = WorkingLength;
while ( LengthCount-- ) {
/* Add each byte in turn into the checksum accumulator */
Checksum += (unsigned int) *WorkingPtr++;
}
} while ( WorkingLength );
/* Report the result */
printf("The checksum is: %u\n", Checksum);
exit(0);
}
/* Report the result */
printf("The checksum is: %u\n", Checksum);
exit(0);
}
```
That brings us to the fourth reason: avoiding an internal-buffered
implementation like Listing 1.5 because of the difficulty of coding such
@ -122,56 +124,58 @@ the design has been maxed out.
**LISTING 1.6 L1-6.C**
/*
* Program to calculate the 16-bit checksum of the stream of bytes
* from the specified file. Buffers the bytes internally, rather
* than letting C or DOS do the work, with the time-critical
* portion of the code written in optimized assembler.
*/
#include <stdio.h>
#include <fcntl.h>
#include <alloc.h> /* alloc.h for Borland,
malloc.h for Microsoft */
```c
/*
* Program to calculate the 16-bit checksum of the stream of bytes
* from the specified file. Buffers the bytes internally, rather
* than letting C or DOS do the work, with the time-critical
* portion of the code written in optimized assembler.
*/
#include <stdio.h>
#include <fcntl.h>
#include <alloc.h> /* alloc.h for Borland,
malloc.h for Microsoft */
#define BUFFER_SIZE 0x8000 /* 32K data buffer */
#define BUFFER_SIZE 0x8000 /* 32K data buffer */
main(int argc, char *argv[]) {
int Handle;
unsigned int Checksum;
unsigned char *WorkingBuffer;
int WorkingLength;
main(int argc, char *argv[]) {
int Handle;
unsigned int Checksum;
unsigned char *WorkingBuffer;
int WorkingLength;
if ( argc != 2 ) {
printf("usage: checksum filename\n");
exit(1);
}
if ( (Handle = open(argv[1], O_RDONLY | O_BINARY)) == -1 ) {
printf("Can't open file: %s\n", argv[1]);
exit(1);
}
if ( argc != 2 ) {
printf("usage: checksum filename\n");
exit(1);
}
if ( (Handle = open(argv[1], O_RDONLY | O_BINARY)) == -1 ) {
printf("Can't open file: %s\n", argv[1]);
exit(1);
}
/* Get memory in which to buffer the data */
if ( (WorkingBuffer = malloc(BUFFER_SIZE)) == NULL ) {
printf("Can't get enough memory\n");
exit(1);
}
/* Get memory in which to buffer the data */
if ( (WorkingBuffer = malloc(BUFFER_SIZE)) == NULL ) {
printf("Can't get enough memory\n");
exit(1);
}
/* Initialize the checksum accumulator */
Checksum = 0;
/* Initialize the checksum accumulator */
Checksum = 0;
/* Process the file in 32K chunks */
do {
if ( (WorkingLength = read(Handle, WorkingBuffer,
BUFFER_SIZE)) == -1 ) {
printf("Error reading file %s\n", argv[1]);
exit(1);
}
/* Checksum this chunk if there's anything in it */
if ( WorkingLength )
ChecksumChunk(WorkingBuffer, WorkingLength, &Checksum);
} while ( WorkingLength );
/* Process the file in 32K chunks */
do {
if ( (WorkingLength = read(Handle, WorkingBuffer,
BUFFER_SIZE)) == -1 ) {
printf("Error reading file %s\n", argv[1]);
exit(1);
}
/* Checksum this chunk if there's anything in it */
if ( WorkingLength )
ChecksumChunk(WorkingBuffer, WorkingLength, &Checksum);
} while ( WorkingLength );
/* Report the result */
printf("The checksum is: %u\n", Checksum);
exit(0);
}
/* Report the result */
printf("The checksum is: %u\n", Checksum);
exit(0);
}
```