Open
Description
Hi for example i want send jpeg image from ESP32 camera (through for example MQTT) using Json, so i must encode jpeg data as base64. And its vaste of memory store jpeg in memory again even bigger because encoded as base64. So i patched ArduinoJson library to do it incrementaly
i created Abstract class DynamicData
class DynamicData {
public:
typedef std::function<void(const char* s, size_t n)> WriteJsonFunc;
typedef std::function<void(const uint8_t* s, size_t n)> WriteRawFunc;
virtual void writeJsonTo(WriteJsonFunc writeFunc) = 0;
virtual void writeRawTo(WriteRawFunc writeFunc) {}
virtual size_t sizeJson() {
return 0;
}
virtual size_t sizeRaw() {
return 0;
}
};
writeJsonTo write data for Json serializer using pointer to write func
writeRawTo write data for MessagePack serializer using pointer to write func
and then i for example create Base64 encoder inherited from Dynamic data and i use it
#include <ArduinoJson.h>
#include <stdio.h>
class Base64 : public DynamicData {
public:
Base64(const char* data, size_t size) : data(data), dataSize(size) {}
Base64() : data(0), dataSize(0) {}
void encodeTriplet(const char (&input)[3], char (&output)[4]) {
output[0] = base64_chars[(input[0] & 0xfc) >> 2];
output[1] =
base64_chars[((input[0] & 0x03) << 4) + ((input[1] & 0xf0) >> 4)];
output[2] =
base64_chars[((input[1] & 0x0f) << 2) + ((input[2] & 0xc0) >> 6)];
output[3] = base64_chars[input[2] & 0x3f];
}
virtual size_t sizeRaw() {
return dataSize;
}
virtual size_t sizeJson() {
return 4 * (1 + ((sizeRaw() - 1) / 3));
}
virtual void writeJsonTo(DynamicData::WriteJsonFunc writer) {
uint j = 0;
char input[3];
char output[4];
for (uint i = 0; i < sizeRaw(); ++i) {
input[j++] = data[i];
if (j == 3) {
encodeTriplet(input, output);
writer(output, 4);
j = 0;
}
}
if (j != 0) {
for (uint i = j; i < 3; ++i) {
input[i] = '\0';
}
encodeTriplet(input, output);
for (uint i = j + 1; i < 4; ++i) {
output[i] = '=';
}
writer(output, 4);
}
}
private:
const char* data;
size_t dataSize;
static const char* base64_chars;
};
const char* Base64::base64_chars =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
int main() {
char output[1280];
const char binaryData[] =
"test big data in memory which cand be stored encoded as base64 again "
"because we must save memory!!";
size_t size =
strlen(binaryData); // only for example (i must know size of binary data)
DynamicJsonDocument doc(1024);
doc["sensor"] = "gps";
doc["binary"] = Base64(binaryData, size);
serializeJson(doc, output);
printf("%s\n ", output);
return 0;
}
and after compile and run i got
{"sensor":"gps","binary":"dGVzdCBiaWcgZGF0YSBpbiBtZW1vcnkgd2hpY2ggY2FuZCBiZSBzdG9yZWQgZW5jb2RlZCBhcyBiYXNlNjQgYWdhaW4gYmVjYXVzZSB3ZSBtdXN0IHNhdmUgbWVtb3J5ISE="}
so it works perfectelly.
Do you want patch ? It is usefull for others ?
it is in my fork ...