Mouseferatu
Hero
His move is not ended until he has squares left to move. And charges happen by the most direct route possible, not necessarily a straight line.
I'm going to have to agree with Draco, here. There's no hard and fast ruling--obviously, or this discussion would be a lot shorter

Look at the rules for Readying, PHB 291. "If you want to use a readied action to attack before an enemy attacks, you should ready your action in response to the enemy's movement. That way your attack will be triggered by a portion of the enemy's move, and you will interrupt it and attack first."
Look at the part I highlighted: a "portion" of the move. The enemy can still go ahead and continue the move afterward.
Moving on. "Note that an enemy might use a power that lets it move and then attack. If you readied an action to attack in response to that enemy's movement, your readied action interrupts the movement, and you can attack before the enemy does."
Again, let's look at the phrase I emphasized: "Interrupts the movement." Not "ends the movement."
Now, weave through the fray isn't a readied action, but it is an immediate reaction--just like a readied action. And it's triggered "when an enemy moves adjacent." So yes, it's the act of moving adjacent that activates it--not "the end of the enemy's movement." And the attack in a charge does not occur until the move has ended. That's something determined, well, when the move ends; it's not "Square X," as determined when the charge started.
I can see no reason why one immediate interrupt would interrupt the movement, but another would end it. If the charging creature has squares of movement left after the ranger shifts, yes, absolutely, he can continue the charge. And if he can still reach you with that movement, then yes, he can still attack.