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111 lines
2.4 KiB
C++
111 lines
2.4 KiB
C++
// Demo of rewriting a line read by fgets
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#include <SPI.h>
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#include "SdFat.h"
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// SD card chip select pin
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const uint8_t chipSelect = SS;
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// file system
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SdFat sd;
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// print stream
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ArduinoOutStream cout(Serial);
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//------------------------------------------------------------------------------
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// store error strings in flash memory
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#define error(s) sd.errorHalt(F(s))
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//------------------------------------------------------------------------------
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void demoFgets() {
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char line[25];
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int c;
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uint32_t pos;
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// open test file
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SdFile rdfile("fgets.txt", O_RDWR);
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// check for open error
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if (!rdfile.isOpen()) {
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error("demoFgets");
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}
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// list file
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cout << F("-----Before Rewrite\r\n");
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while ((c = rdfile.read()) >= 0) {
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Serial.write(c);
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}
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rdfile.rewind();
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// read lines from the file to get position
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while (1) {
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pos = rdfile.curPosition();
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if (rdfile.fgets(line, sizeof(line)) < 0) {
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error("Line not found");
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}
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// find line that contains "Line C"
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if (strstr(line, "Line C")) {
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break;
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}
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}
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// rewrite line with 'C'
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if (!rdfile.seekSet(pos)) {
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error("seekSet");
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}
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rdfile.println("Line R");
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rdfile.rewind();
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// list file
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cout << F("\r\n-----After Rewrite\r\n");
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while ((c = rdfile.read()) >= 0) {
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Serial.write(c);
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}
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// close so rewrite is not lost
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rdfile.close();
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}
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//------------------------------------------------------------------------------
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void makeTestFile() {
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// create or open test file
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SdFile wrfile("fgets.txt", O_WRITE | O_CREAT | O_TRUNC);
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// check for open error
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if (!wrfile.isOpen()) {
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error("MakeTestFile");
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}
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// write test file
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wrfile.print(F(
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"Line A\r\n"
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"Line B\r\n"
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"Line C\r\n"
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"Line D\r\n"
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"Line E\r\n"
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));
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wrfile.close();
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}
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//------------------------------------------------------------------------------
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void setup() {
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Serial.begin(9600);
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// Wait for USB Serial
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while (!Serial) {
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SysCall::yield();
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}
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cout << F("Type any character to start\n");
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while (!Serial.available()) {
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SysCall::yield();
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}
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// Initialize at the highest speed supported by the board that is
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// not over 50 MHz. Try a lower speed if SPI errors occur.
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if (!sd.begin(chipSelect, SD_SCK_MHZ(50))) {
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sd.initErrorHalt();
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}
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makeTestFile();
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demoFgets();
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cout << F("\nDone\n");
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}
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void loop() {}
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