Use case-insensitive comparison for headers fix #2100 (#2101)

* Use case-inseneitive comparison for headers

HTTP headers should be case-insensitive. Use case-insensitive string
comparisons when working with HTTP header responses to ensure
compatibility.

* Revert "Use case-inseneitive comparison for headers"

This reverts commit a02f591723506b62b7208449be6eef7122120398

* Ignore case when searching HTTP header responses

Looking up the Content-Length in the header returned by S3 storage
endpoints should ignore case. To guarantee portability implement a
function for case-insensitive string search, because it is non-standard.

* Add an _ after H5 for the strcasestr implementation

It is a private function and should sport that underscore.

* Remove author comment from the doc comment

* Use search function defined by system if available

Check whether the system provides a function implementing case
insensitive string searches. Only use the custom implementation if the
system does not provide the functionality.

* Add tests for case-insensitive search

Basic tests:
  - Search for empty string
  - Search with exact match
  - Search with case-insensitive match
  - search with no match

* Enforce clang-format style

Some variable definitions in the th5_system tests did not conform to
clang-format's expectations. Updated the offending lines.

* Correct comment describing test case

* Added some spaces to please clang-format

* Ignore discarding const

Ask the compiler to ignore discarding the const when retunring a match from H5_strcasestr

Co-authored-by: Frank Berghaus <frank.berghaus@mpcdf.mpg.de>

4 files changed, 49 insertions, 1 deletions

diff --git a/src/H5FDs3comms.c b/src/H5FDs3comms.c
index 1bf0a2f..628c55a 100644
--- a/src/H5FDs3comms.c
+++ b/src/H5FDs3comms.c
@@ -941,7 +941,7 @@ H5FD_s3comms_s3r_getsize(s3r_t *handle)
      * PARSE RESPONSE *
      ******************/
 
-    start = HDstrstr(headerresponse, "\r\nContent-Length: ");
+    start = HDstrcasestr(headerresponse, "\r\nContent-Length: ");
     if (start == NULL)
         HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "could not find \"Content-Length\" in response.");
 
diff --git a/src/H5private.h b/src/H5private.h
index c2ce4c1..f9ff043 100644
--- a/src/H5private.h
+++ b/src/H5private.h
@@ -593,6 +593,7 @@ H5_DLL herr_t   H5_timer_stop(H5_timer_t *timer /*in,out*/);
 H5_DLL herr_t   H5_timer_get_times(H5_timer_t timer, H5_timevals_t *times /*in,out*/);
 H5_DLL herr_t   H5_timer_get_total_times(H5_timer_t timer, H5_timevals_t *times /*in,out*/);
 H5_DLL char    *H5_timer_get_time_string(double seconds);
+H5_DLL char    *H5_strcasestr(const char *haystack, const char *needle);
 
 /* Depth of object copy */
 typedef enum {
@@ -1385,6 +1386,13 @@ H5_DLL H5_ATTR_CONST int Nflock(int fd, int operation);
 #ifndef HDstrcat
 #define HDstrcat(X, Y) strcat(X, Y)
 #endif
+#ifndef HDstrcasestr
+#if defined(H5_HAVE_STRCASESTR)
+#define HDstrcasestr(X, Y) strcasestr(X, Y)
+#else
+#define HDstrcasestr(X, Y) H5_strcasestr(X, Y)
+#endif
+#endif
 #ifndef HDstrchr
 #define HDstrchr(S, C) strchr(S, C)
 #endif
diff --git a/src/H5system.c b/src/H5system.c
index 9a19860..a7f2edd 100644
--- a/src/H5system.c
+++ b/src/H5system.c
@@ -1350,3 +1350,42 @@ H5_get_option(int argc, const char *const *argv, const char *opts, const struct
     /* return the current flag character found */
     return optchar;
 }
+
+/*-------------------------------------------------------------------------
+ * Function:    H5_strcasestr
+ *
+ * Purpose:     Find the first occurrence of the substring needle in the
+ *              string haystack ignoring case.
+ *
+ * Return:      Success:  Pointer to the beginning of the located substring
+ *
+ *              Failure:  NULL
+ *
+ *-------------------------------------------------------------------------
+ */
+char *
+H5_strcasestr(const char *haystack, const char *needle)
+{
+    /* Check arguments. */
+    HDassert(haystack);
+    HDassert(needle);
+
+    /* begin once from each character of haystack, until needle is found */
+    do {
+        const char *h = haystack;
+        const char *n = needle;
+        /* loop while lowercase strings match, or needle ends */
+        while (HDtolower(*h) == HDtolower(*n) && *n) {
+            h++;
+            n++;
+        }
+        /* if all characters in needle matched we found it */
+        if (*n == 0) {
+            /* must discard const qualifier here, so turn off the warning */
+            H5_GCC_CLANG_DIAG_OFF("cast-qual")
+            return (char *)haystack;
+            H5_GCC_CLANG_DIAG_ON("cast-qual")
+        }
+    } while (*haystack++);
+    return 0;
+} /* end H5_strcasestr() */
diff --git a/src/H5win32defs.h b/src/H5win32defs.h
index 1039f23..ea607da 100644
--- a/src/H5win32defs.h
+++ b/src/H5win32defs.h
@@ -82,6 +82,7 @@ struct timezone {
 #define HDsleep(S)            Sleep(S * 1000)
 #define HDstat(S, B)          _stati64(S, B)
 #define HDstrcasecmp(A, B)    _stricmp(A, B)
+#define HDstrcasestr(A, B)    StrStrIA(A, B)
 #define HDstrndup(S, N)       H5_strndup(S, N)
 #define HDstrtok_r(X, Y, Z)   strtok_s(X, Y, Z)
 #define HDtzset()             _tzset()