bcut.c

#include "util.h"
#include "load.h"
#include "dump.h"

#define DESCRIPTION "select some columns\n\n"
#define USAGE "... | bcut COL1,...,COLN\n\n"
#define EXAMPLE ">> echo a,b,c | bsv | bcut 3,3,3,2,2,1 | csv\nc,c,c,b,b,a\n"

int main(int argc, char **argv) {

    // setup bsv
    SETUP();
    readbuf_t rbuf = rbuf_init((FILE*[]){stdin}, 1, false);
    writebuf_t wbuf = wbuf_init((FILE*[]){stdout}, 1, false);

    // setup state
    i32 num_fields = 0;
    i32 indices[MAX_COLUMNS];
    i32 index;
    ASSERT(argc == 2, "usage: %s", USAGE);
    char *f;
    char *fs = (char*)argv[1];
    while ((f = strsep(&fs, ","))) {
        index = atoi(f);
        indices[num_fields++] = index - 1;
        ASSERT(index <= MAX_COLUMNS, "fatal: cannot select indices above %d, tried to select: %d\n", MAX_COLUMNS, index);
        ASSERT(index > 0, "fatal: indices must be gte 0, got: %d", index);
    }
    ASSERT(num_fields <= MAX_COLUMNS, "fatal: cannot select more than %d indices\n", MAX_COLUMNS);
    row_t row;
    row_t new;

    // process input row by row
    while (1) {
        load_next(&rbuf, &row, 0);
        if (row.stop)
            break;
        for (i32 i = 0; i < num_fields; i++) {
            index = indices[i];
            ASSERT(index <= row.max, "fatal: line with %d columns, needed %d\n", row.max + 1, index + 1);
            new.columns[i] = row.columns[index];
            new.sizes[i] = row.sizes[index];
        }
        new.max = num_fields - 1;
        dump(&wbuf, &new, 0);
    }
    dump_flush(&wbuf, 0);
}