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https://github.com/Alcaro/Flips.git
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60 lines
1.4 KiB
C++
60 lines
1.4 KiB
C++
#include "patch.h"
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namespace patch {
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type identify(const file& patch)
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{
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byte head[16];
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size_t len = patch.read(arrayview<byte>(head));
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if (len>=5 && !memcmp(head, "PATCH", 5)) return t_ips;
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if (len>=4 && !memcmp(head, "UPS1", 4)) return t_ups;
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if (len>=4 && !memcmp(head, "BPS1", 4)) return t_bps;
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return t_unknown;
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}
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type identify_ext(cstring path)
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{
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if (path.endswith(".ips")) return t_ips;
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if (path.endswith(".ups")) return t_ups;
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if (path.endswith(".bps")) return t_bps;
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return t_unknown;
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}
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bool memstream::bpsnum(size_t* out)
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{
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//similar to uleb128, but bpsnum adds another 1<<shift for every byte except the first
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//this ensures there's only one way to encode an integer
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//(other than -0, but this one decodes only unsigned)
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//heavily optimized, so it looks a bit weird
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uint8_t b = *(at++);
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if (LIKELY(b&0x80))
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{
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*out = b ^ (1<<7);
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return true;
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}
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size_t tmp = b;
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b = *(at++);
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tmp |= b<<7;
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if (LIKELY(b&0x80))
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{
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*out = tmp + (1<<7) - (1<<7<<7);
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return true;
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}
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//these weird subtractions and additions wouldn't be needed if the 0x80 bits were inverted
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//but I can't change the BPS spec, so they'll have to stay
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size_t ret = tmp + (1<<7) + (1<<7<<7);
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size_t shift = 7+7;
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while (true)
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{
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uint8_t next = *(at++);
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if (safeint<size_t>::lslov(next^0x80, shift, &tmp)) return false;
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if (safeint<size_t>::addov(ret, tmp, &ret)) return false;
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if (next&0x80) break;
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shift+=7;
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}
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*out = ret;
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return true;
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}
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}
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