dj(1): Refactor out Io_fdseek entirely
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parent
66ca4b9a12
commit
944feef434
95
src/dj.c
95
src/dj.c
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@ -129,52 +129,6 @@ Io_fdopen(struct Io *io, char *fn){
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return fd;
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}
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/* Seeks io->seek bytes through *io's file descriptor, subtracting the number
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* of sought bytes from io->seek. This procedure leaves garbage in io->buf.
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* Read/written bytes here aren't counted in the statistics because successful
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* seeking is guaranteed. */
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static void
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Io_fdseek(struct Io *io){
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assert(io != NULL);
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assert(io->fd != STDIN_FILENO || io->fl == read_flags);
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assert(io->fd != STDOUT_FILENO || io->fl == write_flags);
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if(io->seek == 0
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|| (!fdisstd(io->fd) && lseek(io->fd, io->seek, SEEK_SET) != -1)){
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io->seek = 0;
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return;
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}
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if(io->fl == write_flags)
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memset(io->buf, '\0', io->bs);
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if(io->fl == write_flags){
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memset(io->buf, '\0', io->bs);
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/* We're going to cheat and use bufuse as the retval for write(2),
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* which is fine because it'll be zeroed as this function returns
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* anyway. */
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do{
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if((io->bufuse = write(io->fd, io->buf, MIN(io->bs, io->seek)))
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== 0)
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/* second chance */
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io->bufuse = write(io->fd, io->buf, MIN(io->bs, io->seek));
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}while((io->seek -= io->bufuse) > 0 && io->bufuse != 0);
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}else if(io->fl == read_flags){
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do{
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if((io->bufuse = read(io->fd, io->buf, MIN(io->bs, io->seek)))
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== 0)
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/* second chance */
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io->bufuse = read(io->fd, io->buf, MIN(io->bs, io->seek));
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}while((io->seek -= io->bufuse) > 0 && io->bufuse != 0);
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}else
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assert(0); /* UNREACHABLE */
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io->bufuse = 0;
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return;
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}
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/* Reads io->bs bytes from *io's file descriptor into io->buf, storing the
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* number of read bytes in io->bufuse and updating io->bytes. If io->bufuse is
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* 0, errno will probably be set. Returns io. */
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@ -307,23 +261,60 @@ int main(int argc, char *argv[]){
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}
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}
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assert(io->fd != STDIN_FILENO || io->fl == read_flags);
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assert(io->fd != STDOUT_FILENO || io->fl == write_flags);
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if(argc > optind){
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return usage(program_name);
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}
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for(i = 0; i < 2; ++i){
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/* buffer allocation */
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if((io[i].buf = malloc(io[i].bs * (sizeof *(io[i].buf)))) == NULL){
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fprintf(stderr, "%s: Failed to allocate %d bytes\n",
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program_name, io[i].bs);
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return EX_OSERR;
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}else if(io[i].seek > 0){
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Io_fdseek(&io[i]);
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if(io[i].seek > 0){
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}
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/* easy seeking */
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if(!fdisstd(io[i].fd) && lseek(io[i].fd, io[i].seek, SEEK_SET) != -1)
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io[i].seek = 0;
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}
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/* hard skipping */
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if(io[0].seek > 0){
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do{
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if((io[0].bufuse = read(
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io[0].fd, io[0].buf, MIN(io[0].bs, io[0].seek)))
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== 0)
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/* second chance */
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io->bufuse = read(
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io[0].fd, io[0].buf, MIN(io[0].bs, io[0].seek));
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}while((io[0].seek -= io[0].bufuse) > 0 && io[0].bufuse != 0);
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io[0].bufuse = 0;
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}
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/* hard seeking */
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if(io[1].seek > 0){
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memset(io[1].buf, '\0', io[1].bs);
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/* We're going to cheat and use bufuse as the retval for write(2),
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* which is fine because it'll be zeroed as this function returns
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* anyway. */
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do{
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if((io[1].bufuse = write(
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io[1].fd, io[1].buf, MIN(io[1].bs, io[1].seek)))
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== 0)
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/* second chance */
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io[1].bufuse = write(
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io[1].fd, io[1].buf, MIN(io[1].bs, io[1].seek));
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}while((io[1].seek -= io[1].bufuse) > 0 && io[1].bufuse != 0);
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io[1].bufuse = 0;
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}
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/* Sought bytes aren't counted in the statistics because successful seeking
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* is guaranteed here. */
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for(i = 0; i < 2; ++i)
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if(io[i].seek > 0)
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return oserr(io[i].fn);
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}
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}
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}
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do{ /* read */
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Io_read(&io[0]);
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