Bitcoin source code study

1 where is the code for subsidy cut in half every 4 years

src/validation.cpp, line 1128

============================================================================
CAmount GetBlockSubsidy(int nHeight, const Consensus::Params& consensusParams)
{
int halvings = nHeight / consensusParams.nSubsidyHalvingInterval;
// Force block reward to zero when right shift is undefined.
if (halvings >= 64)
return 0;

CAmount nSubsidy = 50 * COIN;
// Subsidy is cut in half every 210,000 blocks which will occur approximately every 4 years.
nSubsidy >>= halvings;
return nSubsidy;

}

============================================================================

2 where is 21 million hard cap .

src/amount.h

============================================================================
/** Amount in satoshis (Can be negative) */
typedef int64_t CAmount;

static const CAmount COIN = 100000000;
static const CAmount CENT = 1000000;

/** No amount larger than this (in satoshi) is valid.

• Note that this constant is not the total money supply, which in Bitcoin
• currently happens to be less than 21,000,000 BTC for various reasons, but
• rather a sanity check. As this sanity check is used by consensus-critical
• validation code, the exact value of the MAX_MONEY constant is consensus
• critical; in unusual circumstances like a(nother) overflow bug that allowed
• for the creation of coins out of thin air modification could lead to a fork.
• */
  static const CAmount MAX_MONEY = 21000000 * COIN;
  inline bool MoneyRange(const CAmount& nValue) { return (nValue >= 0 && nValue <= MAX_MONEY); }

============================================================================