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diff --git a/docs/opcodes/opcode-21-array-length.html b/docs/opcodes/opcode-21-array-length.html new file mode 100644 index 000000000..576774215 --- /dev/null +++ b/docs/opcodes/opcode-21-array-length.html @@ -0,0 +1,78 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> + +<html> + +<head> +<title>array-length</title> +<link rel=stylesheet href="opcode.css"> +</head> + +<body> + +<h1>array-length</h1> + +<h2>Purpose</h2> + +<p> +Store in the given destination register the length of the indicated array, +in entries. +</p> + +<h2>Details</h2> + +<table class="instruc"> +<thead> +<tr> + <th>Op & Format</th> + <th>Mnemonic / Syntax</th> + <th>Arguments</th> +</tr> +</thead> +<tbody> +<tr> + <td>21 12x</td> + <td>array-length vA, vB</td> + <td><code>A:</code> destination register (4 bits)<br/> + <code>B:</code> array reference-bearing register (4 bits)</td> +</tr> +</tbody> +</table> + +<h2>Constraints</h2> + +<ul> + <li> + Both A and B must be valid register indices for the current stack frame. + </li> + <li> + Register vB must contain a reference to an array. + </li> +</ul> + +<h2>Behavior</h2> + +<ul> + <li> + The length of the array referenced by vB is stored in vA, that is + vA' = length(vB). + </li> + <li> + If register v(A-1) is the lower half of a register pair, register v(A-1)' + becomes undefined. + </li> + <li> + If register v(A+1) is the upper half of a register pair, register v(A+1)' + becomes undefined. + </li> +</ul> + +<h2>Exceptions</h2> + +<ul> + <li> + NullPointerException is thrown if the value of register vB is null. + </li> +</ul> + +</body> +</html> |