include/vbyte2.h File Reference

#include <stdio.h>

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Functions
unsigned int	vbyte_read (FILE *fp, unsigned long int *n)
unsigned int	vbyte_write (FILE *fp, unsigned long int n)
unsigned int	vbyte_scan (FILE *fp)
unsigned int	vbyte_len (unsigned long int n)

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Function Documentation

unsigned int vbyte_len

(

unsigned long int

n

)

Definition at line 111 of file vbyte2.c.

                                            {
    unsigned int ret = 1;
    while (n >= 128) {
        n >>= 7;
        ret++;
    }
    return ret;
}

unsigned int vbyte_read	(	FILE *	fp,
		unsigned long int *	n
	)

Definition at line 19 of file vbyte2.c.

Referenced by get_list_at(), and get_next_lo_info().

                                                        {
    unsigned int ret = 1;
    unsigned int count = 0; 
    uint8_t byte;

    *n = 0;
    while (fread(&byte, 1, 1, fp)) {
        if (byte & 0x80) {
            /* For each time we get a group of 7 bits, need to left-shift the 
               latest group by an additional 7 places, since the groups were 
               effectively stored in reverse order.*/
            *n |= ((byte & 0x7f) << count);
            ret++;
            count += 7;
        } else if (ret > (sizeof(*n))) {
            if (ret == (sizeof(*n) + 1) 
              && (byte < (1 << (sizeof(*n) + 1)))) {
                /* its a large, but valid number */
                *n |= byte << count;
                return ret;
            } else {
                /* we've overflowed */

                /* pretend we detected it as it happened */
                fseek(fp, - (int) (ret - (sizeof(*n) + 1)), SEEK_CUR);
                errno = EOVERFLOW;
                return 0;
            }
        } else {
            *n |= byte << count;
            return ret;
        }
    }

    /* got a read error */
    return 0;
}

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unsigned int vbyte_scan

(

FILE *

fp

)

Definition at line 79 of file vbyte2.c.

                                  {
    unsigned int ret = 1;
    uint8_t byte;

    while (fread(&byte, 1, 1, fp)) {
        if (byte & 0x80) {
            /* For each time we get a group of 7 bits, need to left-shift the 
               latest group by an additional 7 places, since the groups were 
               effectively stored in reverse order.*/
            ret++;
        } else if (ret > sizeof(unsigned long int)) {
            if (ret == (sizeof(unsigned long int) + 1) 
              && (byte < (1 << (sizeof(unsigned long int) + 1)))) {
                /* its a large, but valid number */
                return ret;
            } else {
                /* we've overflowed */

                /* pretend we detected it as it happened */
                fseek(fp, - (int) (ret - (sizeof(unsigned long int) + 1)), SEEK_CUR);
                errno = EOVERFLOW;
                return 0;
            }
        } else {
            return ret;
        }
    }

    /* got a read error */
    return 0;
}

unsigned int vbyte_write	(	FILE *	fp,
		unsigned long int	n
	)

Definition at line 57 of file vbyte2.c.

                                                        {
    unsigned int ret = 1;
    uint8_t byte;

    while (n >= 128) {
        /* write the bytes out least significant to most significant */
        byte = (uint8_t) (n & 0x7f) | 0x80;
        if (!fwrite(&byte, 1, 1, fp)) {
            return 0;
        }
        n >>= 7;
        ret++;
    }

    byte = (uint8_t) n;
    if (!fwrite(&byte, 1, 1, fp)) {
        return 0;
    }
    
    return ret;
}

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