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jd2833
Joined: 28 Mar 2011
Posts: 2
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| Convert part of a string to int |
 Posted: Mon Mar 28, 2011 12:49 pm |
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I have a beginner problem that I'd like some help with.
My program reads in a directory listing from an SD card. The files found can have any file name, and are stored (one by one) in the string fname[]. E.g.:
| Code: | file.txt
STC001.txt
STC004.txt
STC005.txt
thumbs.db |
The program is looking for files starting with "STC", then 3 digits, and then the extension ".txt". It needs to find the last file in the list, irrespective of any gaps in the sequence (e.g. there is no file STC002.txt), increase the file number by one, and put the resulting filename in a string.
For example, the value of fname[] after processing the above file list should be "STC006.txt".
To detect if the filename matches my criteria, I was thinking of scanning through the filename string in three parts; one to detect if the filename starts with 'STC', another scan to read the digits, and another scan to check if the extension is '.txt'.
| Code: | char const STC[] = "STC";
char const DTXT[] = ".TXT";
int8 x;
//check if file starts with "STC"
for (x = 0; (x < 3) && (STC[x] == toupper(finfo.fname[x])) && finfo.fname[x]; x++);
if (x == 3) { //filename starts with "STC"
//check if next 3 characters are 0..9
for (; (x < 6) && isdigit((finfo.fname[x])) && finfo.fname[x]; x++) {
//put read values in int here
}
if (x == 6) { //3 digits read
//check if next 4 characters are the correct extension '.txt'
for (; (x < 10) && (DTXT[x] == toupper(finfo.fname[x])) && finfo.fname[x]; x++);
if (x != 10)
FilenameValid = TRUE;
}
}
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This leaves me to devise a way to put the detected digits into an integer variable, and to check if the file number is higher than the previous one.
But I bet the more experienced programmers can whip up a smarter and more compact solution. Care to give it a go? Thanks in advance! |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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jd2833
Joined: 28 Mar 2011
Posts: 2
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| Posted: Tue Mar 29, 2011 3:37 am |
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Thanks for the hints. I solved it in the following way:
| Code: | char *FindLastFile(char *ptr) {
DIR dir;
FILINFO finfo;
FRESULT result; // FatFs function common result code
BOOLEAN done;
char tempstr[13];
int8 x;
char const CorrectFile[]="STC.TXT";
int16 LastFile=0;
//go through all files in directory
for (done = FALSE;!done;) {
result = f_readdir(&dir, &finfo);
if (result != FR_OK) {
printf(usb_cdc_putc, "FILE SYSTEM ERROR - \r\n");
return 0;
}
// finished ?? (no more files in directory)
if (!finfo.fname[0]) {
done = TRUE;
} else {
//extract first 3 chars from filename (should match "STC")
memcpy(tempstr, finfo.fname, 3);
//extract last 4 chars from filename (should match ".TXT")
memcpy(&tempstr[3], &finfo.fname[6], 4);
//terminate string
tempstr[7] = '\0';
//check if tempstring == "STC.TXT"
for (x=0; (x < 7) && (CorrectFile[x] == toupper(tempstr[x])) && tempstr[x]; x++);
//if filename matches "STCxxx.TXT"
if (x == 7) {
//extract numbers from filename
memcpy(&tempstr[0], &finfo.fname[3], 3);
//terminate string
tempstr[3] = '\0';
//check if extracted characters are in fact digits
for (x=0; isdigit(tempstr[x]); x++);
if (x == 3) {
if (atol(tempstr)>LastFile) {
LastFile=atol(tempstr);
}
printf(usb_cdc_putc, "isdigit! tempstr: %s, atol: %ld, LastFile: %ld\r\n",
tempstr, atol(tempstr), LastFile);
} else {
printf(usb_cdc_putc, "nodigit! tempstr: %s, atol: %ld\r\n", tempstr, atol(tempstr));
}
}
}
}
sprintf(tempstr, "STC%03ld.TXT", LastFile+1);
return tempstr;
}
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If anything can be improved or done in a more efficient way then I'm always happy to hear feedback! |
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