Sort a list of object identifiers: Difference between revisions

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 {{out}}
 <pre>1.3.6.1.4.1.11.2.17.5.2.0.79
+.3.6.1.4.1.11.2.17.19.3.4.0.1
+.3.6.1.4.1.11.2.17.19.3.4.0.4
+.3.6.1.4.1.11.2.17.19.3.4.0.10
+.3.6.1.4.1.11150.3.4.0
+.3.6.1.4.1.11150.3.4.0.1
+</pre>
+=={{header|C}}==
+A C99 (or later) compiler is required.
+<lang cpp>#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+typedef struct oid_tag
+{
+    char* str_;
+    int* numbers_;
+    int length_;
+} oid;
+// free memory, no-op if p is null
+void oid_destroy(oid* p)
+{
+    if (p != 0)
+    {
+        free(p->str_);
+        free(p->numbers_);
+        free(p);
+    }
+}
+int char_count(const char* str, char ch)
+{
+    int count = 0;
+    for (const char* p = str; *p; ++p)
+    {
+        if (*p == ch)
+            ++count;
+    }
+    return count;
+}
+// construct an OID from a string
+// returns 0 on memory allocation failure or parse error
+oid* oid_create(const char* str)
+{
+    oid* ptr = calloc(1, sizeof(oid));
+    if (ptr == 0)
+        return 0;
+    ptr->str_ = strdup(str);
+    if (ptr->str_ == 0)
+    {
+        oid_destroy(ptr);
+        return 0;
+    }
+    int dots = char_count(str, '.');
+    ptr->numbers_ = malloc(sizeof(int) * (dots + 1));
+    if (ptr->numbers_ == 0)
+    {
+        oid_destroy(ptr);
+        return 0;
+    }
+    ptr->length_ = dots + 1;
+    const char* p = str;
+    for (int i = 0; i <= dots && *p;)
+    {
+        char* eptr = 0;
+        int num = strtol(p, &eptr, 10);
+        if (*eptr != 0 && *eptr != '.')
+        {
+            // TODO: check for overflow/underflow
+            oid_destroy(ptr);
+            return 0;
+        }
+        ptr->numbers_[i++] = num;
+        p = eptr;
+        if (*p)
+            ++p;
+    }
+    return ptr;
+}
+// compare two OIDs
+int oid_compare(const void* p1, const void* p2)
+{
+    const oid* o1 = *(oid* const*)p1;
+    const oid* o2 = *(oid* const*)p2;
+    int i1 = 0, i2 = 0;
+    for (; i1 < o1->length_ && i2 < o2->length_; ++i1, ++i2)
+    {
+        if (o1->numbers_[i1] < o2->numbers_[i2])
+            return -1;
+        if (o1->numbers_[i1] > o2->numbers_[i2])
+            return 1;
+    }
+    if (o1->length_ < o2->length_)
+        return -1;
+    if (o1->length_ > o2->length_)
+        return 1;
+    return 0;
+}
+int main()
+{
+    const char* input[] = {
+        "1.3.6.1.4.1.11.2.17.19.3.4.0.10",
+        "1.3.6.1.4.1.11.2.17.5.2.0.79",
+        "1.3.6.1.4.1.11.2.17.19.3.4.0.4",
+        "1.3.6.1.4.1.11150.3.4.0.1",
+        "1.3.6.1.4.1.11.2.17.19.3.4.0.1",
+        "1.3.6.1.4.1.11150.3.4.0"
+    };
+    const int len = sizeof(input)/sizeof(input[0]);
+    oid* oids[len] = { 0 };
+    int i;
+    for (i = 0; i < len; ++i)
+    {
+        oids[i] = oid_create(input[i]);
+        if (oids[i] == 0)
+        {
+            fprintf(stderr, "Out of memory\n");
+            goto cleanup;
+        }
+    }
+    qsort(oids, len, sizeof(oid*), oid_compare);
+    for (i = 0; i < len; ++i)
+        puts(oids[i]->str_);
+cleanup:
+    for (i = 0; i < len; ++i)
+        oid_destroy(oids[i]);
+    return 0;
+}</lang>
+{{out}}
+<pre>
+.3.6.1.4.1.11.2.17.5.2.0.79
 .3.6.1.4.1.11.2.17.19.3.4.0.1
 .3.6.1.4.1.11.2.17.19.3.4.0.4