diff options
authorRich Felker <>2015-12-20 00:32:46 -0500
committerRich Felker <>2015-12-20 00:39:35 -0500
commitc673158d91ad995ed59dd910777cd6464f61fe8e (patch)
parentd87f0a9a95f0a1228ee5579e5822a8c93bc96823 (diff)
fix overly pessimistic realloc strategy in getdelim
previously, getdelim was allocating twice the space needed every time it expanded its buffer to implement exponential buffer growth (in order to avoid quadratic run time). however, this doubling was performed even when the final buffer length needed was already known, which is the common case that occurs whenever the delimiter is in the FILE's buffer. this patch makes two changes to remedy the situation: 1. over-allocation is no longer performed if the delimiter has already been found when realloc is needed. 2. growth factor is reduced from 2x to 1.5x to reduce the relative excess allocation in cases where the delimiter is not initially in the buffer, including unbuffered streams. in theory these changes could lead to quadratic time if the same buffer is reused to process a sequence of lines successively increasing in length, but once this length exceeds the stdio buffer size, the delimiter will not be found in the buffer right away and exponential growth will still kick in.
1 files changed, 1 insertions, 1 deletions
diff --git a/src/stdio/getdelim.c b/src/stdio/getdelim.c
index 813b09fc..1ccd8029 100644
--- a/src/stdio/getdelim.c
+++ b/src/stdio/getdelim.c
@@ -30,7 +30,7 @@ ssize_t getdelim(char **restrict s, size_t *restrict n, int delim, FILE *restric
if (i+k+1 >= *n) {
if (k >= SIZE_MAX/2-i) goto oom;
size_t m = i+k+2;
- if (m < SIZE_MAX/4) m *= 2;
+ if (!z && m < SIZE_MAX/4) m += m/2;
tmp = realloc(*s, m);
if (!tmp) {
m = i+k+2;