elm_entry: Speedup finding new line, prevent readind invalid memory

Summary:
1- Speed up detecting new lines.
```
if (!strncmp(text, "<br", 3) || !strncmp(text, "<ps", 3))
```
This will cause 6 comparisons (if one of conditions did not meet), or at least 3 comparisons.

this is changed to
```
if (!strncmp(text, "<", 1))
```

2- Speedup detecting lines

If this condition is true, we should increment the string for next iteration 3 times, not just one
```
if (!strncmp(text, "<br", 3) || !strncmp(text, "<ps", 3))
```

if '<' founded then 'pr' or 'br', we will skip 3 characters for next iteration.

```
if (!strncmp(text, "<", 1))
      {
         text++;
         len--;
         if (!strncmp(text, "br", 2) || !strncmp(text, "ps", 2))
         {
            text += 2;
            len -= 2;
```

3- Prevent reading invalid memory out of the string

```
if (text[3] == '>' || ((text[3] == '/') && (text[4] == '>')))
```
string could reach last char in string (original string ends with "<br")

but now we will check if remaining string length allow comparison :

```
if (text[0] == '>' || (len > 1 && ((text[0] == '/') && (text[1] == '>'))))
```

Test Plan:
```

static int

oldFunc(const char *text)
{
    if (!text)
        return 0;

    while (*text)
    {
        if (!strncmp(text, "<br", 3) || !strncmp(text, "<ps", 3))
        {
            if (text[3] == '>' || ((text[3] == '/') && (text[4] == '>')))
            {
                return 1;
            }
        }
        text++;
    }
    return 0;
}

static int
newFunc(const char *text)
{
    if (!text)
        return 0;
    char *pTemp = (char *)text;

    while (pTemp = strchr(pTemp, '<'))
    {
        pTemp++;
        if (!strncmp(pTemp, "br", 2) || !strncmp(pTemp, "ps", 2))
        {
            pTemp += 2;
            if (pTemp[0] != '\0' && (pTemp[0] == '>' || (pTemp[0] == '/' && pTemp[1] == '>')))
            {
                return 1;
            }
        }
    }

    return 0;
}

int main()
{

    int counter = 1000;
    srand(time(NULL));
    char pStr[50001] = {0};
    char AllChars[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789<>";

    int AllCharsLen = strlen(AllChars);
    for (int i = 0; i < 50000; i++)
        pStr[i] = AllChars[rand() % AllCharsLen];

    clock_t start, end;
    double total_Time1 = 0;
    int i;

    for (int j = 0; j < 3; j++)
    {
        if (j == 0)
        {
            printf("random String\n");
        }
        else if (j == 1)
        {
            printf("With Random <br/>\n");
            int location = rand()%(5000 - 5);
            pStr[location++] = '<';
            pStr[location++] = 'b';
            pStr[location++] = 'r';
            pStr[location++] = '/';
            pStr[location++] = '>';
        }
        else if (j == 2)
        {
            printf("With Random <ps>\n");
            int location = rand()%(5000 - 4);
            pStr[location++] = '<';
            pStr[location++] = 'p';
            pStr[location++] = 's';
            pStr[location++] = '>';
        }

        start = clock();
        for (i = 0; i < counter; i++)
            oldFunc(pStr);
        end = clock();
        total_Time1 = ((double)(end - start)) / CLOCKS_PER_SEC;
        printf("original = %f has new Line = %i\n", total_Time1, oldFunc(pStr));

        start = clock();
        for (i = 0; i < counter; i++)
            newFunc(pStr);
        end = clock();
        total_Time1 = ((double)(end - start)) / CLOCKS_PER_SEC;
        printf("modified = %f has new line = %i\n\n", total_Time1, newFunc(pStr));
    }
}
```

output:

random String
original = 2.523000 has new Line = 0
modified = 0.090000 has new line = 0

With Random <br/>
original = 0.081000 has new Line = 1
modified = 0.003000 has new line = 1

With Random <ps>
original = 0.016000 has new Line = 1
modified = 0.001000 has new line = 1

Reviewers: zmike, woohyun, bowonryu

Reviewed By: zmike

Subscribers: bu5hm4n, segfaultxavi, zmike, cedric, #reviewers, #committers

Tags: #efl

Differential Revision: https://phab.enlightenment.org/D8497

1 files changed, 13 insertions, 11 deletions

diff --git a/src/lib/elementary/elm_entry.c b/src/lib/elementary/elm_entry.c
index e48a8c8ecb..5543504a3d 100644
--- a/src/lib/elementary/elm_entry.c
+++ b/src/lib/elementary/elm_entry.c
@@ -2868,18 +2868,20 @@ _entry_has_new_line(const char *text)
 {
    if (!text) return EINA_FALSE;
 
-   while (*text)
-     {
-        if (!strncmp(text, "<br", 3) || !strncmp(text, "<ps", 3))
-          {
-             if (text[3] == '>' || ((text[3] == '/') && (text[4] == '>')))
-               {
-                  return EINA_TRUE;
-               }
-          }
-        text++;
-     }
+   const char * pTemp = text;
 
+   while ((pTemp = strchr(pTemp, '<')))
+   {
+      pTemp++;
+      if (!strncmp(pTemp, "br", 2) || !strncmp(pTemp, "ps", 2))
+      {
+         pTemp += 2;
+         if (pTemp[0] != '\0' && (pTemp[0] == '>' || (pTemp[0] == '/' && pTemp[1] == '>')))
+         {
+            return EINA_TRUE;
+         }
+      }
+   }
    return EINA_FALSE;
 }