buf.h (raw) (1720B)
1 /* A piece chain implementation. 2 gearsix, 2022 */ 3 #ifndef PIECETABLE 4 #define PIECETABLE 5 6 #ifdef __cplusplus 7 extern "C" { 8 #endif 9 10 11 #include <stdio.h> 12 13 /* Points to a file (`f`), which contains a string that starts at 14 `off`, with length of `len`. `prev` and `next` point to the 15 previous and next items in the table. */ 16 typedef struct Piece { 17 FILE *f; 18 size_t off, len; 19 struct Piece *prev, *next; 20 } Piece; 21 22 /* Holds a doubly-linked `Piece` list, starting at `tail`, ending at 23 `head`. `pos` points to the last addressed `Piece`. `size` is the 24 sum length of all `len` values of all `Piece` items in the list. 25 `idx` is the last addressed index in the chain. `read` and `append` 26 point to the original file and any data to be added. */ 27 typedef struct Buf { 28 FILE *read, *append; 29 size_t size, idx; 30 struct Piece *tail, *pos, *head; 31 } Buf; 32 33 /* Allocates & initialises a `Buf`. If `append` is NULL, nothing is 34 allocated or initialised and NULL is returned. */ 35 Buf * 36 bufinit(FILE *read, FILE *append); 37 38 /* Frees `b` and all `Piece` items associated with it. */ 39 void 40 buffree(Buf *b); 41 42 /* Set `b->idx` to `pos` and `b->pos` to the `Piece` in the chain, 43 where the start of `b->pos->next` is `pos`. */ 44 Piece * 45 bufidx(Buf *b, size_t pos); 46 47 /* Adds a new `Piece` to the chain, at `pos` (found using `bufidx`). 48 `s` will be appended to `b->append` and the new `Piece` will 49 reflect the appended data. */ 50 size_t 51 bufins(Buf *b, size_t pos, const char *s); 52 53 /* Removed all pieces from index `pos` to `pos+num`. `pos` and 54 `pos+num` are found using `bufidx`. */ 55 size_t 56 bufdel(Buf *b, size_t pos, int num); 57 58 /* writes all data in `b` to `f`. */ 59 size_t 60 bufout(Buf *b, FILE *f); 61 62 63 #ifdef __cplusplus 64 } 65 #endif 66 67 #endif /* PIECETABLE */