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Address to optimized QR string #581

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merged 8 commits into from May 6, 2021
Merged

Address to optimized QR string #581

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b9d5200
Access Display and Formatter with fmt:: like in other places
RCasatta Mar 22, 2021
d18554e
Address to string conversion optimized for qr codes
RCasatta Mar 22, 2021
cac3f46
improve to_qr_string doc
RCasatta Mar 23, 2021
104836a
implements alternate formatting for address
RCasatta Apr 7, 2021
85ae82f
use the char trick to avoid allocation
RCasatta Apr 7, 2021
bc406bf
Use &mut dyn fmt::Write instead of bool
Kixunil Apr 9, 2021
3158ced
document alternate formatting
RCasatta Apr 9, 2021
0a91496
rename to_qr_string into to_qr_uri returning also the schema
RCasatta Apr 15, 2021
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24 changes: 14 additions & 10 deletions src/util/address.rs
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Expand Up @@ -353,20 +353,24 @@ impl Address {
self.payload.script_pubkey()
}

/// Creates a string optimized to be encoded in QR codes, meaning it becomes uppercase if bech32.
/// Creates a URI string *bitcoin:address* optimized to be encoded in QR codes.
///
/// If the address is bech32, both the schema and the address become uppercase.
/// If the address is base58, the schema is lowercase and the address is left mixed case.
///
/// Quoting BIP 173 "inside QR codes uppercase SHOULD be used, as those permit the use of
/// alphanumeric mode, which is 45% more compact than the normal byte mode."
/// Even inside Bitcoin URI may be more efficient to use the uppercase address since in QR codes
/// encoding modes can be mixed as needed within a QR symbol.
///
/// This `fn` is a shorthand of the alternate formatting `{:#}` which should be preferred in most
/// cases because it avoids the [String] allocation.
pub fn to_qr_string(&self) -> String {
format!("{:#}", self)
pub fn to_qr_uri(&self) -> String {
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Still not sure about the best naming, since the function returns URI string, not URI object

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It's good enough imo, I'm no fan of unneccesarily duplicating the signature in the name and the returned string is a valid URI.

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I was thinking about this too since if we later add URI, then This will suck.

However, in reality, if you call a method like this you probably want to display it or encode it (e.g. using serde), not inspect its contents in the same way you would after parsing. It may be not beautiful, but it's pragmatic.

let schema = match self.payload {
Payload::WitnessProgram { .. } => "BITCOIN",
_ => "bitcoin",
};
format!("{}:{:#}", schema, self)
}
}

// Alternate formatting `{:#}` is used to return uppercase version of bech32 addresses which should
// be used in QR codes, see [Address::to_qr_uri]
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I suggest informing the readers of best practices:

s/see [Address::to_qr_uri]/please use [Address::to_qr_uri] unless you really have to avoid alocation/

impl fmt::Display for Address {
fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
match self.payload {
Expand Down Expand Up @@ -779,12 +783,12 @@ mod tests {
fn test_qr_string() {
for el in ["132F25rTsvBdp9JzLLBHP5mvGY66i1xdiM", "33iFwdLuRpW1uK1RTRqsoi8rR4NpDzk66k"].iter() {
let addr = Address::from_str(el).unwrap();
assert_eq!(addr.to_qr_string(), *el);
assert_eq!(addr.to_qr_uri(), format!("bitcoin:{}", el));
}

for el in ["bcrt1q2nfxmhd4n3c8834pj72xagvyr9gl57n5r94fsl", "bc1qwqdg6squsna38e46795at95yu9atm8azzmyvckulcc7kytlcckxswvvzej"].iter() {
let addr = Address::from_str(el).unwrap();
assert_eq!(addr.to_qr_string(), el.to_ascii_uppercase());
assert_eq!(addr.to_qr_uri(), format!("BITCOIN:{}", el.to_ascii_uppercase()) );
}
}

Expand Down