c/c++语言开发共享C – 尝试返回文件中的上一行

您可以跳过处理您不感兴趣的行：

 for (i = 0; i < (cIn-1); i++){ while (fgets(buffer, 4999, inputFiles[i])){ if(buffer[0] == '@' || buffer[0] == '>') { puts(buffer); } /* else do nothing*/ } } 

然后你只需要替换puts(buffer); 使用您需要处理有效行的代码。 （尽管如此，从您的示例来看，您似乎只想忽略以#开头的行，？）

而不是fgetpos(); fsetpos(); fgetpos(); fsetpos(); 你可能会用
fseek(inputFiles[i], -strlen(buffer), SEEK_CUR);

（恕我直言）Best是将整个文件读入一个大缓冲区（mmap也是一个选项，如果可用），然后查找并修复行结尾和fasta标题。 这也将减少内存碎片。 它大大简化了’解析器’。

编辑：添加源（它不完美，但上次我检查它，它工作;-)可能不完整，我从一个更大的程序剪断它。

 struct fastapart { char * name; char * data; unsigned size; struct roedel *friends; }; struct fastafile { size_t totsize; char *tot; unsigned count; struct fastapart *parts; int *alloc; }; struct fastafile * read_complete_fasta(char *name) { int rc,state; struct fastafile * result; size_t pos,len,cnt,idx; struct strbuff *fwd=NULL,*rev = NULL; result = malloc (sizeof *result); if (!result) return NULL; result->tot = read_complete_file(name , &result->totsize); if (!result->tot) goto failfree; result->count = 0; result->parts = NULL; for (pos=cnt=state=0; pos < result->totsize; ) { switch (state) { case 0: /* find first '>' */ if (result->tot[pos] == '>') { pos++; state=2; continue; } pos += strcspn( result->tot+pos, "n" ); case 1: /* not found: sync to newline */ if (result->tot[pos] == 'n') { pos++; state=0; continue; } else pos++; continue;; case 2: /* Got '>'; grab name */ len = strcspn( result->tot+pos, " tn" ); if (cnt >= result->count) { size_t siz; siz = result->count ? 2* result->count: 16; result->parts = realloc( result->parts , siz * sizeof *result->parts); for ( ; result->count < siz;result->count ++) { result->parts[cnt].name = NULL; result->parts[cnt].data = NULL; result->parts[cnt].friends = NULL; result->parts[cnt].size = 0; } } result->parts[cnt].name = result->tot+pos; result->parts[cnt].name[len] = 0; pos += 1+len; len = strspn( result->tot+pos, " tn" ); pos += len; state++; continue; case 3: /* grab data; for the moment, throw away reversed data */ if (result->tot[pos] == '>') { if (fwd) { memcpy(result->parts[cnt].data, fwd->data, fwd->used ); result->parts[cnt].size = fwd->used; result->parts[cnt].data [ fwd->used ] = 0; fwd->used = 0; } if (rev) { /* memcpy(result->parts[cnt].data+result->parts[cnt].size, rev->data, rev->used ); */ rev->used = 0; } if (result->parts[cnt].data) cnt++; pos++; state=2; continue; } len = strcspn( result->tot+pos, "tn" ); if (!len) { /* empty line; what to do? skip it! */ fprintf(stderr, "Emptyn" ); pos++; state=1; continue; } if (!result->parts[cnt].data) {result->parts[cnt].data = result->tot+pos; } fwd = strbuff_add(fwd, result->tot+pos, len); pos += len; if (result->tot[pos] == 't' ) { pos += strspn(result->tot+pos, " t" ); len = strcspn( result->tot+pos, "n" ); rev = strbuff_add(rev, result->tot+pos, len); pos += len; } pos += strspn(result->tot+pos, " trn" ); }} if (state == 3) { if (fwd) { memcpy(result->parts[cnt].data, fwd->data, fwd->used ); result->parts[cnt].size = fwd->used; result->parts[cnt].data [ fwd->used ] = 0; fwd->used = 0; } if (rev) { /* memcpy(result->parts[cnt].data+result->parts[cnt].size, rev->data, rev->used ); */ rev->used = 0; } if (result->parts[cnt].data) cnt++; } /* final realloc */ result->parts = realloc( result->parts, cnt * sizeof *result->parts); result->count = cnt; free (fwd); free (rev); result->alloc = malloc( result->count * sizeof result->alloc[0] ); if (result->alloc) { for (cnt = 0; cnt < result->count; cnt++ ) result->alloc[cnt] = cnt; } return result; failfree: free (fwd); free (rev); free (result); return NULL; } char * read_complete_file(char *name, size_t *sizep) { int fd, rc; size_t size, len; char *result; struct stat st; fd = open(name, O_RDONLY); if (fd == -1) goto fail; rc = fstat(fd, &st); if (rc == -1) goto closefail; result = malloc (1+st.st_size ); if (!result ) goto closefail; result[st.st_size] = 0; for (size = 0; size < st.st_size;) { rc = read(fd, result, st.st_size - size); if (rc < 0) goto freeclosefail; size += rc; } fprintf(stderr, "Read %lu bytes FROM %sn" , (unsigned long) size, name); close(fd); *sizep = size; return result; freeclosefail: free(result); closefail: close(fd); fail: *sizep=0; return NULL; }