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Generalize ConvertBits to permit transforming the input

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This commit is contained in:
Pieter Wuille
2022-04-04 11:58:54 -04:00
committed by MacroFake
parent 78f3ac51b7
commit 1a72d62152
1 changed files with 14 additions and 3 deletions
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17
src/util/strencodings.h
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@@ -249,15 +249,26 @@ bool TimingResistantEqual(const T& a, const T& b)
*/
[[nodiscard]] bool ParseFixedPoint(const std::string &val, int decimals, int64_t *amount_out);
namespace {
/** Helper class for the default infn argument to ConvertBits (just returns the input). */
struct IntIdentity
{
[[maybe_unused]] int operator()(int x) const { return x; }
};
} // namespace
/** Convert from one power-of-2 number base to another. */
template<int frombits, int tobits, bool pad, typename O, typename I>
bool ConvertBits(const O& outfn, I it, I end) {
template<int frombits, int tobits, bool pad, typename O, typename It, typename I = IntIdentity>
bool ConvertBits(O outfn, It it, It end, I infn = {}) {
size_t acc = 0;
size_t bits = 0;
constexpr size_t maxv = (1 << tobits) - 1;
constexpr size_t max_acc = (1 << (frombits + tobits - 1)) - 1;
while (it != end) {
acc = ((acc << frombits) | *it) & max_acc;
int v = infn(*it);
if (v < 0) return false;
acc = ((acc << frombits) | v) & max_acc;
bits += frombits;
while (bits >= tobits) {
bits -= tobits;