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Avoid extra copying and simplify hexdump()

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This commit is contained in:
dmiller 2026-08-31 16:17:40 +00:00
parent 794d1aff28
commit 08a074881b
1 changed files with 15 additions and 18 deletions
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33
nbase/nbase_misc.c
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@ -605,6 +605,7 @@ unsigned long nbase_adler32(const unsigned char *buf, int len)
#undef ADLER32_BASE
static const char hexch[] = "0123456789abcdef";
/* This function returns a string containing the hexdump of the supplied
* buffer. It uses current locale to determine if a character is printable or
* not. It prints 73char+\n wide lines like these:
@ -618,25 +619,23 @@ unsigned long nbase_adler32(const unsigned char *buf, int len)
* that the caller is supposed to free().
* */
char *hexdump(const u8 *cp, u32 length){
static char asciify[257]; /* Stores character table */
static char asciify[256]; /* Stores character table */
int asc_init=0; /* Flag to generate table only once */
u32 i=0, hex=0, asc=0; /* Array indexes */
u32 line_count=0; /* For byte count at line start */
char *current_line=NULL; /* Current line to write */
char *buffer=NULL; /* Dynamic buffer we return */
#define LINE_LEN 74 /* Length of printed line */
char line2print[LINE_LEN]; /* Stores current line */
char printbyte[16]; /* For byte conversion */
char *line2print; /* Start of current line */
int bytes2alloc; /* For buffer */
memset(line2print, ' ', LINE_LEN); /* We fill the line with spaces */
/* On the first run, generate a list of nice printable characters
* (according to current locale) */
if( asc_init==0){
asc_init=1;
for(i=0; i<256; i++){
if( isalnum(i) || isdigit(i) || ispunct(i) ){ asciify[i]=i; }
else{ asciify[i]='.'; }
memset(asciify, '.', sizeof(asciify));
for (i=0; i<0xff; i++) {
if (isgraph(i)) {
asciify[i]=i;
}
}
}
/* Allocate enough space to print the hex dump */
@ -646,7 +645,8 @@ char *hexdump(const u8 *cp, u32 length){
}
bytes2alloc=(length%16==0)? (1 + LINE_LEN * (length/16)) : (1 + LINE_LEN * (1+(length/16))) ;
buffer=(char *)safe_zalloc(bytes2alloc);
current_line=buffer;
memset(buffer, ' ', bytes2alloc - 1); /* Fill line with spaces */
line2print=buffer;
#define HEX_START 7
#define ASC_START 57
/* This is how or line looks like.
@ -659,23 +659,20 @@ char *hexdump(const u8 *cp, u32 length){
*/
i=0;
while( i < length ){
memset(line2print, ' ', LINE_LEN); /* Fill line with spaces */
snprintf(line2print, sizeof(line2print), "%04x", (16*line_count++) % 0xFFFF); /* Add line No.*/
snprintf(line2print, 5, "%04x", i & 0xFFFF); /* Add line No.*/
line2print[4]=' '; /* Replace the '\0' inserted by snprintf() with a space */
hex=HEX_START; asc=ASC_START;
do { /* Print 16 bytes in both hex and ascii */
if (i%16 == 8) hex++; /* Insert space every 8 bytes */
snprintf(printbyte, sizeof(printbyte), "%02x", cp[i]);/* First print the hex number */
line2print[hex++]=printbyte[0];
line2print[hex++]=printbyte[1];
line2print[hex++]=' ';
line2print[hex++]=hexch[(cp[i] >> 4) & 0xf];
line2print[hex++]=hexch[cp[i] & 0xf];
hex++; /* ' ' */
line2print[asc++]=asciify[ cp[i] ]; /* Then print its ASCII equivalent */
i++;
} while (i < length && i%16 != 0);
/* Copy line to output buffer */
line2print[LINE_LEN-1]='\n';
memcpy(current_line, line2print, LINE_LEN);
current_line += LINE_LEN;
line2print += LINE_LEN;
}
buffer[bytes2alloc-1]='\0';
return buffer;