		Search-engine friendly clone of the ACL2 documentation.

States32

Read32-mem-ubyte16-lendian

Read an unsigned 16-bit little endian integer from memory.

Signature
(read32-mem-ubyte16-lendian addr stat) → val
Arguments: addr — Guard (integerp addr).; stat — Guard (state32p stat).
Returns: val — Type (ubyte16p val).

We read the byte at the given address, and the byte at the address just after, which could be 0 if the given address is the last one in the space. We put the two bytes together in little endian order.

Definitions and Theorems

Function: read32-mem-ubyte16-lendian

(defun read32-mem-ubyte16-lendian (addr stat)
  (declare (xargs :guard (and (integerp addr) (state32p stat))))
  (let ((__function__ 'read32-mem-ubyte16-lendian))
    (declare (ignorable __function__))
    (b* ((b0 (read32-mem-ubyte8 addr stat))
         (b1 (read32-mem-ubyte8 (1+ (ifix addr))
                                stat)))
      (+ b0 (ash b1 8)))))

Theorem: ubyte16p-of-read32-mem-ubyte16-lendian

(defthm ubyte16p-of-read32-mem-ubyte16-lendian
  (b* ((val (read32-mem-ubyte16-lendian addr stat)))
    (ubyte16p val))
  :rule-classes :rewrite)

Theorem: read32-mem-ubyte16-lendian-of-ifix-addr

(defthm read32-mem-ubyte16-lendian-of-ifix-addr
  (equal (read32-mem-ubyte16-lendian (ifix addr)
                                     stat)
         (read32-mem-ubyte16-lendian addr stat)))

Theorem: read32-mem-ubyte16-lendian-int-equiv-congruence-on-addr

(defthm read32-mem-ubyte16-lendian-int-equiv-congruence-on-addr
  (implies (acl2::int-equiv addr addr-equiv)
           (equal (read32-mem-ubyte16-lendian addr stat)
                  (read32-mem-ubyte16-lendian addr-equiv stat)))
  :rule-classes :congruence)

Theorem: read32-mem-ubyte16-lendian-of-state32-fix-stat

(defthm read32-mem-ubyte16-lendian-of-state32-fix-stat
  (equal (read32-mem-ubyte16-lendian addr (state32-fix stat))
         (read32-mem-ubyte16-lendian addr stat)))

Theorem: read32-mem-ubyte16-lendian-state32-equiv-congruence-on-stat

(defthm read32-mem-ubyte16-lendian-state32-equiv-congruence-on-stat
  (implies (state32-equiv stat stat-equiv)
           (equal (read32-mem-ubyte16-lendian addr stat)
                  (read32-mem-ubyte16-lendian addr stat-equiv)))
  :rule-classes :congruence)