[hackers] [sbase] sort: reuse buffer in columns() || Hiltjo Posthuma

[git]

commit 72250324b1af5c8d7d9a036fe8860252487a533f
Author: Hiltjo Posthuma <hil...@codemadness.org>
Date:   Tue May 5 13:41:43 2015 +0200

    sort: reuse buffer in columns()
    
    speeds up sorting for huge input aswell.

diff --git a/sort.c b/sort.c
index 901189e..8ec14c3 100644
--- a/sort.c
+++ b/sort.c
@@ -38,10 +38,12 @@ static int parse_keydef(struct keydef *, char *, int);
 static char *skipblank(char *);
 static char *skipnonblank(char *);
 static char *skipcolumn(char *, char *, int);
-static char *columns(char *, const struct keydef *);
+static size_t columns(char *, const struct keydef *, char **, size_t *);
 
 static int Cflag = 0, cflag = 0, uflag = 0;
 static char *fieldsep = NULL;
+static char *col1, *col2;
+static size_t col1siz, col2siz;
 
 static void
 addkeydef(char *def, int flags)
@@ -81,32 +83,28 @@ check(FILE *fp)
 static int
 linecmp(const char **a, const char **b)
 {
-       char *s1, *s2;
        int res = 0;
        long double x, y;
        struct kdlist *node;
 
        for (node = head; node && res == 0; node = node->next) {
-               s1 = columns((char *)*a, &node->keydef);
-               s2 = columns((char *)*b, &node->keydef);
+               columns((char *)*a, &node->keydef, &col1, &col1siz);
+               columns((char *)*b, &node->keydef, &col2, &col2siz);
 
                /* if -u is given, don't use default key definition
                 * unless it is the only one */
                if (uflag && node == tail && head != tail) {
                        res = 0;
                } else if (node->keydef.flags & MOD_N) {
-                       x = strtold(s1, NULL);
-                       y = strtold(s2, NULL);
+                       x = strtold(col1, NULL);
+                       y = strtold(col2, NULL);
                        res = x < y ? -1 : x > y;
                } else {
-                       res = strcmp(s1, s2);
+                       res = strcmp(col1, col2);
                }
 
                if (node->keydef.flags & MOD_R)
                        res = -res;
-
-               free(s1);
-               free(s2);
        }
 
        return res;
@@ -202,10 +200,11 @@ skipcolumn(char *s, char *eol, int next_col)
        return s;
 }
 
-static char *
-columns(char *line, const struct keydef *kd)
+static size_t
+columns(char *line, const struct keydef *kd, char **col, size_t *colsiz)
 {
        char *start, *end, *eol = strchr(line, '\n');
+       size_t len;
        int i;
 
        for (i = 1, start = line; i < kd->start_column; i++)
@@ -226,7 +225,14 @@ columns(char *line, const struct keydef *kd)
        } else {
                end = eol;
        }
-       return enstrndup(2, start, start > end ? 0 : end - start);
+       len = start > end ? 0 : end - start;
+       if (!*col || *colsiz < len)
+               *col = erealloc(*col, len + 1);
+       memcpy(*col, start, len);
+       (*col)[len] = '\0';
+       if (*colsiz < len)
+               *colsiz = len;
+       return len;
 }
 
 static void
@@ -258,7 +264,7 @@ main(int argc, char *argv[])
                addkeydef(EARGF(usage()), global_flags);
                break;
        case 'm':
-               /* more or less for free, but for perfomance-reasons,
+               /* more or less for free, but for performance-reasons,
                 * we should keep this flag in mind and maybe some later
                 * day implement it properly so we don't run out of memory
                 * while merging large sorted files.