57 lines
1.6 KiB
C++
57 lines
1.6 KiB
C++
/*
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* Rewrite Example
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*
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* This sketch shows how to rewrite part of a line in the middle
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* of the file created by the SdFatAppend.pde example.
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*
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* Check around line 30 of pass 50 of APPEND.TXT after running this sketch.
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*/
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#include <SdFat.h>
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#include <SdFatUtil.h> // use functions to print strings from flash memory
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const uint8_t SD_CHIP_SELECT = SS;
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SdFat sd;
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SdFile file;
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// store error strings in flash to save RAM
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#define error(s) sd.errorHalt_P(PSTR(s))
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void setup(void) {
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Serial.begin(9600);
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while (!Serial) {} // wait for Leonardo
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PgmPrintln("Type any character to start");
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while (Serial.read() <= 0) {}
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delay(200); // Catch Due reset problem
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// initialize the SD card at SPI_HALF_SPEED to avoid bus errors with
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// breadboards. use SPI_FULL_SPEED for better performance.
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if (!sd.begin(SD_CHIP_SELECT, SPI_HALF_SPEED)) sd.initErrorHalt();
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char name[] = "APPEND.TXT";
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// open for read and write
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if (!file.open(name, O_RDWR)) {
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PgmPrint("Can't open ");
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Serial.println(name);
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PgmPrintln("Run the append example to create the file.");
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error("file.open failed");
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}
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// seek to middle of file
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if (!file.seekSet(file.fileSize()/2)) error("file.seekSet failed");
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// find end of line
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int16_t c;
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while ((c = file.read()) > 0 && c != '\n');
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if (c < 0) error("file.read failed");
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// clear write error flag
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file.writeError = false;
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// rewrite the begining of the line at the current position
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file.write("**rewrite**");
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if (file.writeError) error("file.write failed");
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if (!file.close()) error("file.close failed");
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Serial.print(name);
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PgmPrintln(" rewrite done.");
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}
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void loop(void) {}
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