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psbt: clarify PSBT, PSBTInput, PSBTOutput unserialization flows

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The unserialization flows of the PSBT types work based on few underlying
assumptions of functions from `serialize.h` & `stream.h` that takes some
to understand when read the first time.

Add few comments that highlight these assumptions hopefully making it easier
to grasp. Also, mention key/value format types as per BIP 174.
This commit is contained in:
rkrux 2025-05-05 17:04:27 +05:30
parent fa2c548429
commit d31158d364
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GPG Key ID: 8614B8BD2E144C6D
1 changed files with 18 additions and 9 deletions
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27
src/psbt.h
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@ -465,7 +465,8 @@ struct PSBTInput
// Read loop
bool found_sep = false;
while(!s.empty()) {
// Read
// Read the key of format "<keylen><keytype><keydata>" after which
// "key" will contain "<keytype><keydata>"
std::vector<unsigned char> key;
s >> key;
@ -476,11 +477,13 @@ struct PSBTInput
break;
}
// Type is compact size uint at beginning of key
// "skey" is used so that "key" is unchanged after reading keytype below
SpanReader skey{key};
// keytype is of the format compact size uint at the beginning of "key"
uint64_t type = ReadCompactSize(skey);
// Do stuff based on type
// Do stuff based on keytype "type", i.e., key checks, reading values of the
// format "<valuelen><valuedata>" from the stream "s", and value checks
switch(type) {
case PSBT_IN_NON_WITNESS_UTXO:
{
@ -949,7 +952,8 @@ struct PSBTOutput
// Read loop
bool found_sep = false;
while(!s.empty()) {
// Read
// Read the key of format "<keylen><keytype><keydata>" after which
// "key" will contain "<keytype><keydata>"
std::vector<unsigned char> key;
s >> key;
@ -960,11 +964,13 @@ struct PSBTOutput
break;
}
// Type is compact size uint at beginning of key
// "skey" is used so that "key" is unchanged after reading keytype below
SpanReader skey{key};
// keytype is of the format compact size uint at the beginning of "key"
uint64_t type = ReadCompactSize(skey);
// Do stuff based on type
// Do stuff based on keytype "type", i.e., key checks, reading values of the
// format "<valuelen><valuedata>" from the stream "s", and value checks
switch(type) {
case PSBT_OUT_REDEEMSCRIPT:
{
@ -1212,7 +1218,8 @@ struct PartiallySignedTransaction
// Read global data
bool found_sep = false;
while(!s.empty()) {
// Read
// Read the key of format "<keylen><keytype><keydata>" after which
// "key" will contain "<keytype><keydata>"
std::vector<unsigned char> key;
s >> key;
@ -1223,11 +1230,13 @@ struct PartiallySignedTransaction
break;
}
// Type is compact size uint at beginning of key
// "skey" is used so that "key" is unchanged after reading keytype below
SpanReader skey{key};
// keytype is of the format compact size uint at the beginning of "key"
uint64_t type = ReadCompactSize(skey);
// Do stuff based on type
// Do stuff based on keytype "type", i.e., key checks, reading values of the
// format "<valuelen><valuedata>" from the stream "s", and value checks
switch(type) {
case PSBT_GLOBAL_UNSIGNED_TX:
{