Digital Signal Processing Library

Voice Lab

Program name: read_data

Language: C

In file: file_lib.c

Objective: Read data from file.

Usage: int read_data(FILE *in_file, int data_size, int sample_rate, int *result);

Parameters:

• in_file - FILE Pointer to open file to process.
• data_size - Length of data word - typically 2 bytes.
• sample_rate - number of bits per sample - typically 16.
• result - data read

• count - should be equal to data_size, typically 2

Mathematical Description:

Comments: Routine is used to read data file and return a value

User Comments

Code:

int read_data(FILE *in_file, int data_size, int sample_rate, int *result)
{
        unsigned char c[4];
        int i, count;

/* read and return the data */
        switch(data_size) {
        case 1:
                count = fread(&c, sizeof(char), data_size, in_file);
                (*result) = (int) c[0];
                break;
        case 2:
                count = fread(&c, sizeof(char), data_size, in_file);
                (*result) = c[0];
                (*result) |= c[1] << 8;
                if(c[1] & 0x80) {
                        for(i = 2; i < sizeof(int); i++) {
                                (*result) |= 0xFF<<(i*8);
                        }
                }
                break;
        case 3:
                count = fread(&c, sizeof(char), data_size, in_file);
                (*result) = c[0];
                (*result) |= c[1] << 8;
                (*result) |= c[2] << 16;
                if(c[2] & 0x80) {
                        for(i = 3; i < sizeof(int); i++) {
                                (*result) |= 0xFF<<(i*8);
                        }
                }
                break;
        case 4:
                count = fread(&c, sizeof(char), data_size, in_file);
                (*result) = c[0];
                (*result) |= c[1] << 8;
                (*result) |= c[2] << 16;
                (*result) |= c[3] << 24;
                if(c[3] & 0x80) {
                        for(i = 4; i < sizeof(int); i++) {
                                (*result) |= 0xFF<<(i*8);
                        }
                }
                break;
        default:
                fprintf(stderr, "Data_length out of range:(%d)! What to do?\n", data_size);
                exit(1);
        }
        return(count);
}