I'm having a strange issue when using the Arduino Giga R1. I'm trying to make a webserver with it, which I've got almost working completely, but if I have any images on the page, the fread() function I'm using to read files from a flash drive seems to read the file, but will stop copying the file into the buffer once it hits the first null byte. I have been able to confirm this by analyzing the original file, and the file I get in my browser using a hex editor. I've tried using fgets() instead, but that function seems to completely fail after reading just a few bytes. I set up the server so that it can serve pretty much any file and notify the browser of the file's type and size. I should also mention, I'm using the Giga's SDRAM chip to act as the buffer. It's 8MB, and the image in question here is only about 2.7MB, so memory capacity isn't the issue here. I have also tried this with different, smaller images, and I'm getting the exact same problem with those, as well. The entire webpage loads just fine (html, js, css files all load correctly), it's only the images that will not load properly. As a possible workaround, I've thought about converting images to base64 before storing them into SDRAM and then transmitting them to the client, but I haven't figured out how to do that yet. I don't even know if that's a viable option. As a side note, I'm starting to believe the entire problem might be related to the Giga's MbedOS. I think the MbedOS implementation on the Giga might be screwing around with read/write functions and erroring out when encountering null bytes.
Here's the code in question:
FILE *f = fopen(filename.c_str(), "rb");
if (f) {
client.println(F("HTTP/1.1 200 OK"));
//client.println(F("Connection: close"));
client.print(F("Content-Type: "));
const char* ext = filename.substring(filename.indexOf(".")).c_str();
Serial.print(F("Extension: "));
Serial.println(ext);
String contentType = getContentType(ext);
Serial.println(contentType);
client.println(contentType);
client.print(F("Content-Length: "));
fseek(f, 0, SEEK_END);
long filesize = ftell(f);
rewind(f);
Serial.print("File size: ");
Serial.println(filesize);
client.println(filesize);
client.println();
char *buffer;
buffer = (char*)SDRAM.malloc(sizeof(char) * (filesize + 1));
//memset(buffer, 'F', sizeof(char) * (filesize + 1));
size_t bytesRead = fread(buffer, sizeof(char), filesize, f);
Serial.print("Bytes read: ");
Serial.println(bytesRead);
Serial.print("buffer size: ");
Serial.println(strlen(buffer));
for (int i = 0; i < strlen(buffer); i++) {
Serial.print(buffer[i], HEX);
}
Serial.println();
client.write(buffer);
client.flush();
fclose(f);
SDRAM.free(buffer);
}
I've also uploaded two images showing the raw data of the original image and the image my browser gets from the Arduino in the hex editor. I have also uploaded a screenshot of the Serial output showing that fread() did in fact read the entire image file, but the final size of the buffer is only 8 bytes, which corresponds to the 8 bytes of the image file just before encountering the first null bytes in the original image.
So, what's going on here? Why does fread() stop copying the image data into the buffer once it encounters the first null byte in the image?
