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Update TLV8.md

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@ -176,29 +176,115 @@ TLV8_it supports the following methods:
* setting *T=uint16_t* with a VALUE byte-array containing 4 bytes return an *incorrect* numeric value
* this function returns zero for all zero-LENGTH TLV8 records
### A detailed example using the above methods
The following code:
```C++
TLV8 myTLV; // instantiates an empty TLV8 object
myTLV.add(1,32000); // add a TLV8 record with TAG=1 and VALUE=32000
auto it_A = myTLV.add(2,180); // add a TLV8 record with TAG=2 and VALUE=18, and save the iterator that is returned
myTLV.add(1,8700); // add a TLV8 record with TAG=1 and VALUE=8700
auto it_A = myTLV.add(2,180); // add a TLV8 record with TAG=2 and VALUE=180, and save the iterator that is returned
uint8_t v[]={0x01, 0x05, 0xE3, 0x4C}; // create a fixed array, v, of 4 bytes
myTLV.add(200,4,v); // add a TLV8 record with TAG=200 and copy all 4 bytes of array v into its VALUE
uint8_t v[32]; // create a 32-byte array, v, and fill it with some data
for(int i=0;i<32;i++)
v[i]=i;
myTLV.add(200,32,v); // add a TLV8 record with TAG=200 and copy all 32 bytes of array v into its VALUE
myTLV.add(50,60000); // add a TLV8 record with TAG=50 and VALUE=60000
myTLV.add(255); // add a zero-length TLV8 record with TAG=255 to act as separator
myTLV.add(50,120000); // add a TLV8 record with TAG=50 and VALUE=120000
myTLV.add(255); // add a zero-length TLV8 record with TAG=255 to act as separator
auto it_B = myTLV.add(50,30000); // add a TLV8 record with TAG=50 and VALUE=30000, and save the iterator that is returned
myTLV.add(50,180000); // add a TLV8 record with TAG=50 and VALUE=180000
myTLV.add(255); // add a zero-length TLV8 record with TAG=255 to act as separator
auto it_B = myTLV.add(50,240000); // add a TLV8 record with TAG=50 and VALUE=240000, and save the iterator that is returned
auto it_C = myTLV.find(50); // find an iterator to the first TLV8 record with TAG=50;
auto it_D = myTLV.find(50,std::next(it_C)); // find an iterator to the first TLV8 record with TAG=50 that occurs AFTER it_C;
auto it_C = myTLV.find(200); // find an iterator to first TLV8 record with TAG=200;
auto it_D = myTLV.find(50); // find an iterator to first TLV8 record with TAG=50;
auto it_E = myTLV.find(200); // find an iterator to first TLV8 record with TAG=200;
myTLV.print(); // prints the contents of myTLV to the Serial Monitor
Serial.printf("results of myTLV.print():\n\n");
myTLV.print(); // print the contents of myTLV to the Serial Monitor
Serial.printf("\n");
// print content of it_A:
Serial.printf("it_A: TAG=%d, LENGTH=%d, Value=%d\n", it_A->getTag(), it_A->getLen(), it_A->getVal());
// print content of it_B using alternative syntax:
Serial.printf("it_B: TAG=%d, LENGTH=%d, Value=%d\n", (*it_B).getTag(), (*it_B).getLen(), (*it_B).getVal());
// print contents of it_C and it_D, based on previous find() above:
Serial.printf("it_C TAG=%d, LENGTH=%d, Value=%d\n", (*it_C).getTag(), (*it_C).getLen(), (*it_C).getVal());
Serial.printf("it_D TAG=%d, LENGTH=%d, Value=%d\n", (*it_D).getTag(), (*it_D).getLen(), (*it_D).getVal());
// you can also use the results of find() directly without saving as a separate iterator, though this is computationally inefficient:
if(myTLV.find(1)!=myTLV.end()) // check for match
Serial.printf("Found: TAG=%d, LENGTH=%d, Value=%d\n", myTLV.find(1)->getTag(), myTLV.find(1)->getLen(), myTLV.find(1)->getVal());
// sum up all the bytes in it_E:
int sum=0;
for(int i=0; i < it_E->getLen(); i++)
sum+= (*it_E)[i];
Serial.printf("it_E TAG=%d, LENGTH=%d, Sum of all bytes = %d\n", (*it_E).getTag(), (*it_E).getLen(), sum);
// create a "blank" TLV8 record with TAG=90 and space for 16 bytes:
auto it_F = myTLV.add(90,16,NULL);
// copy the first 16 bytes of it_E into it_F and print the record:
memcpy(*it_F,*it_E,16);
myTLV.print(it_F);
```
produces the following output:
```C++
results of myTLV.print():
1(2) FC21 [8700]
2(1) B4 [180]
200(32) 000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F
50(2) 60EA [60000]
255(0) [null]
50(4) C0D40100 [120000]
255(0) [null]
50(4) 20BF0200 [180000]
255(0) [null]
50(4) 80A90300 [240000]
it_A: TAG=2, LENGTH=1, Value=180
it_B: TAG=50, LENGTH=4, Value=240000
it_C TAG=50, LENGTH=2, Value=60000
it_D TAG=50, LENGTH=4, Value=120000
Found: TAG=1, LENGTH=2, Value=8700
it_E TAG=200, LENGTH=32, Sum of all bytes = 496
90(16) 000102030405060708090A0B0C0D0E0F
```
## Reading and Writing TLV8 Characteristics
As documented in the [API Reference](Reference.md#spancharacteristicvalue-boolean-nvsstore), the following *SpanCharacteristic* methods are used to read and write TLV8 objects to TLV8 Characteristics:
* `getVal(TLV8 &tlv)`
* `getNewVal(TLV8 &tlv)`
* `setVal(TLV8 &tlv)`
These are analagous to the `getVal()` and `setVal()` methods used for numerical-based Characteristics.
Note that since TLV8 Characteristics are stored as base-64 encoded strings, you can use `getString()` to read the base-64 text, or `getData()` to decode the string into the full byte-array that represents the entire TLV8 object.
Also, if you really don't want to use HomeSpan's TLV8 library to produce TLV8 objects, but instead prefer to use your own methods to create a TLV8-compliant byte-array, you can do so and then use `setData()` to save the byte-array you produced to the TLV8 Characteristic, which will perform the base-64 encoding. Or if you want to additionally perform your own base-64 encoding (why?) you can do so and then simply use `setString()` to save the resulting encoded string to the TLV8 Characteristic.