1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef __PERF_STRBUF_H 3 #define __PERF_STRBUF_H 4 5 /* 6 * Strbuf's can be use in many ways: as a byte array, or to store arbitrary 7 * long, overflow safe strings. 8 * 9 * Strbufs has some invariants that are very important to keep in mind: 10 * 11 * 1. the ->buf member is always malloc-ed, hence strbuf's can be used to 12 * build complex strings/buffers whose final size isn't easily known. 13 * 14 * It is NOT legal to copy the ->buf pointer away. 15 * `strbuf_detach' is the operation that detachs a buffer from its shell 16 * while keeping the shell valid wrt its invariants. 17 * 18 * 2. the ->buf member is a byte array that has at least ->len + 1 bytes 19 * allocated. The extra byte is used to store a '\0', allowing the ->buf 20 * member to be a valid C-string. Every strbuf function ensure this 21 * invariant is preserved. 22 * 23 * Note that it is OK to "play" with the buffer directly if you work it 24 * that way: 25 * 26 * strbuf_grow(sb, SOME_SIZE); 27 * ... Here, the memory array starting at sb->buf, and of length 28 * ... strbuf_avail(sb) is all yours, and you are sure that 29 * ... strbuf_avail(sb) is at least SOME_SIZE. 30 * strbuf_setlen(sb, sb->len + SOME_OTHER_SIZE); 31 * 32 * Of course, SOME_OTHER_SIZE must be smaller or equal to strbuf_avail(sb). 33 * 34 * Doing so is safe, though if it has to be done in many places, adding the 35 * missing API to the strbuf module is the way to go. 36 * 37 * XXX: do _not_ assume that the area that is yours is of size ->alloc - 1 38 * even if it's true in the current implementation. Alloc is somehow a 39 * "private" member that should not be messed with. 40 */ 41 42 #include <assert.h> 43 #include <stdarg.h> 44 #include <stddef.h> 45 #include <string.h> 46 #include <linux/compiler.h> 47 #include <sys/types.h> 48 49 extern char strbuf_slopbuf[]; 50 struct strbuf { 51 size_t alloc; 52 size_t len; 53 char *buf; 54 }; 55 56 #define STRBUF_INIT { 0, 0, strbuf_slopbuf } 57 58 /*----- strbuf life cycle -----*/ 59 int strbuf_init(struct strbuf *buf, ssize_t hint); 60 void strbuf_release(struct strbuf *buf); 61 char *strbuf_detach(struct strbuf *buf, size_t *); 62 63 /*----- strbuf size related -----*/ 64 static inline ssize_t strbuf_avail(const struct strbuf *sb) { 65 return sb->alloc ? sb->alloc - sb->len - 1 : 0; 66 } 67 68 int strbuf_grow(struct strbuf *buf, size_t); 69 70 static inline int strbuf_setlen(struct strbuf *sb, size_t len) { 71 if (!sb->alloc) { 72 int ret = strbuf_grow(sb, 0); 73 if (ret) 74 return ret; 75 } 76 assert(len < sb->alloc); 77 sb->len = len; 78 sb->buf[len] = '\0'; 79 return 0; 80 } 81 82 /*----- add data in your buffer -----*/ 83 int strbuf_addch(struct strbuf *sb, int c); 84 85 int strbuf_add(struct strbuf *buf, const void *, size_t); 86 static inline int strbuf_addstr(struct strbuf *sb, const char *s) { 87 return strbuf_add(sb, s, strlen(s)); 88 } 89 90 int strbuf_addf(struct strbuf *sb, const char *fmt, ...) __printf(2, 3); 91 92 /* XXX: if read fails, any partial read is undone */ 93 ssize_t strbuf_read(struct strbuf *, int fd, ssize_t hint); 94 95 #endif /* __PERF_STRBUF_H */ 96