[Legolas]

The passage as it appears in the movie is actually broken up in the book between Gandalf telling Frodo the story of Sauron and his rings. There are also things that are paraphrased, like the last quote I've given here.

‘Ah!’ said Gandalf. ‘That is a very long story. The beginnings lie back in the Black Years, which only the lore-masters now remember. If I were to tell you all that tale, we should still be sitting here when Spring had passed into Winter.
‘But last night I told you of Sauron the Great, the Dark Lord. The rumours that you have heard are true: he has indeed arisen again and left his hold in Mirkwood and returned to his ancient fastness in the Dark Tower of Mordor. That name even you hobbits have heard of, like a shadow on the borders of old stories. Always after a defeat and a respite, the Shadow takes another shape and grows again.’
‘I wish it need not have happened in my time,’ said Frodo.
‘So do I,’ said Gandalf, ‘and so do all who live to see such times. But that is not for them to decide. All we have to decide is what to do with the time that is given, us. And already, Frodo, our time is beginning to look black. The Enemy is fast becoming very strong. His plans are far from ripe, I think, but they are ripening. We shall be hard put to it. We should be very hard put to it, even if it were not for this dreadful chance.

A bit later...

‘I am sorry,’ said Frodo. ‘But I am frightened; and I do not feel any pity for Gollum.’
‘You have not seen him,’ Gandalf broke in.
‘No, and I don’t want to,’ said Frodo. I can’t understand you. Do you mean to say that you, and the Elves, have let him live on after all those horrible deeds? Now at any rate he is as bad as an Orc, and just an enemy. He deserves death.’
‘Deserves it! I daresay he does. Many that live deserve death. And some that die deserve life. Can you give it to them? Then do not be too eager to deal out death in judgement. For even the very wise cannot see all ends. I have not much hope that Gollum can be cured before he dies, but there is a chance of it. And he is bound up with the fate of the Ring. My heart tells me that he has some part to play yet, for good or ill, before the end; and when that comes, the pity of Bilbo may rule the fate of many - yours not least. In any case we did not kill him: he is very old and very wretched. The Wood-elves have him in prison, but they treat him with such kindness as they can find in their wise hearts.’
‘All the same,’ said Frodo, ‘even if Bilbo could not kill Gollum, I wish he had not kept the Ring. I wish he had never found it, and that I had not got it! Why did you let me keep it? Why didn’t you make me throw it away, or, or destroy it?’
‘Let you? Make you?’ said the wizard. ‘Haven’t you been listening to all that I have said? You are not thinking of what you are saying. But as for throwing it away, that was obviously wrong. These Rings have a way of being found. In evil hands it might have done great evil. Worst of all, it might have fallen into the hands of the Enemy. Indeed it certainly would; for this is the One, and he is exerting all his power to find it or draw it to himself.
‘Of course, my dear Frodo, it was dangerous for you; and that has troubled me deeply. But there was so much at stake that I had to take some risk - though even when I was far away there has never been a day when the Shire has not been guarded by watchful eyes. As long as you never used it, I did not think that the Ring would have any lasting effect on you, not for evil, not at any rate for a very long time. And you must remember that nine years ago, when I last saw you, I still knew little for certain.’

‘I do really wish to destroy it!’ cried Frodo. ‘Or, well, to have it destroyed. I am not made for perilous quests. I wish I had never seen the Ring! Why did it come to me? Why was I chosen?’
‘Such questions cannot be answered,’ said Gandalf. ‘You may be sure that it was not for any merit that others do not possess: not for power or wisdom, at any rate. But you have been chosen, and you must therefore use such strength and heart and wits as you have.’