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/* Saving history in a line-based input stream.
* SRE, Mon Dec 28 09:51:51 2009 [Zaragoza]
#include "esl_config.h"
#include <stdio.h>
#include <sys/types.h>
* A history of a line-based input stream.
* Allows (limited) rewinding in nonrewindable input streams;
* also allows block-based parsing (as opposed to line-based).
* The history is kept in a rolling array of string ptrs. The
* bookkeeping involved in indexing this array can be confusing.
* Lines in the file are numbered 0..N-1.
* (N isn't known; we'll be reading sequentially.)
* Lines in the recorder are 0..nalloc-1.
* The recorder keeps track of how many lines it has read so far, in
* <nread>.
* The recorder can be backed up to any previous line. It sets <ncurr>
* to be the number of lines it *appears* to have read so far;
* that is, the next line it will return to the caller, upon a call
* to esl_recorder_Read(), is line <ncurr>.
* A window of MIN(nread, nalloc) lines is stored;
* consisting of line numbers MAX(baseline, nread-nalloc) .. nread-1).
* A line n in the file (0..n..N-1) corresponds to
* an index i in the recorder by these transforms:
* i = (n-baseline) % nalloc
* n = i + MAX(baseline, nread-nalloc)
* Normally the baseline for the modulo calculation is just 0.
* The line array is circularly permuted (out of order) when
* (nread-baseline) / nalloc != 0.
typedef struct {
FILE *fp; /* stream that we're reading line by line */
char **line; /* lines from input, line[0..nalloc-1] */
int nalloc; /* max number of lines remembered */
int *lalloc; /* alloc for each line[0..nalloc-1][0..lalloc[i]-1] */
off_t *offset; /* disk offsets to starts of each line */
int nread; /* max # of lines read from file in any pass [1..] */
int ncurr; /* # of lines into file in current pass [1..] */
int baseline; /* line origin for n<->i transform [0..] */
int markline; /* line origin for start of current block [-1;0..] */
extern ESL_RECORDER *esl_recorder_Create (FILE *fp, int maxlines);
extern int esl_recorder_ResizeTo (ESL_RECORDER *rc, int new_maxlines);
extern int esl_recorder_GetFirst (ESL_RECORDER *rc);
extern int esl_recorder_GetLast (ESL_RECORDER *rc);
extern int esl_recorder_GetCurrent(ESL_RECORDER *rc);
extern int esl_recorder_GetNext (ESL_RECORDER *rc);
extern void esl_recorder_Destroy (ESL_RECORDER *rc);
extern int esl_recorder_Read(ESL_RECORDER *rc, char **opt_line);
extern int esl_recorder_Position(ESL_RECORDER *rc, int linenumber);
extern int esl_recorder_MarkBlock(ESL_RECORDER *rc, int markline);
extern int esl_recorder_UnmarkBlock(ESL_RECORDER *rc);
extern int esl_recorder_GetBlock(ESL_RECORDER *rc, char ***opt_lines, int **opt_lalloc, off_t **opt_offset, int *opt_nlines);
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