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| 1 | +//! Provides functions for escaping literals and identifiers for use |
| 2 | +//! in SQL queries. |
| 3 | +//! |
| 4 | +//! Prefer parameterized queries where possible; see |
| 5 | +//! [`Client::query`](crate::Client::query). Do not escape parameters. |
| 6 | +
|
| 7 | +#[cfg(test)] |
| 8 | +mod test; |
| 9 | + |
| 10 | +/// Escape a literal and surround result with single quotes. Not |
| 11 | +/// recommended in most cases. |
| 12 | +/// |
| 13 | +/// If input contains backslashes, result will be of the form ` |
| 14 | +/// E'...'` so it is safe to use regardless of the setting of |
| 15 | +/// standard_conforming_strings. |
| 16 | +pub fn escape_literal(input: &str) -> String { |
| 17 | + escape_internal(input, false) |
| 18 | +} |
| 19 | + |
| 20 | +/// Escape an identifier and surround result with double quotes. |
| 21 | +pub fn escape_identifier(input: &str) -> String { |
| 22 | + escape_internal(input, true) |
| 23 | +} |
| 24 | + |
| 25 | +// Translation of PostgreSQL libpq's PQescapeInternal(). Does not |
| 26 | +// require a connection because input string is known to be valid |
| 27 | +// UTF-8. |
| 28 | +// |
| 29 | +// Escape arbitrary strings. If as_ident is true, we escape the |
| 30 | +// result as an identifier; if false, as a literal. The result is |
| 31 | +// returned in a newly allocated buffer. If we fail due to an |
| 32 | +// encoding violation or out of memory condition, we return NULL, |
| 33 | +// storing an error message into conn. |
| 34 | +fn escape_internal(input: &str, as_ident: bool) -> String { |
| 35 | + let mut num_backslashes = 0; |
| 36 | + let mut num_quotes = 0; |
| 37 | + let quote_char = if as_ident { '"' } else { '\'' }; |
| 38 | + |
| 39 | + // Scan the string for characters that must be escaped. |
| 40 | + for ch in input.chars() { |
| 41 | + if ch == quote_char { |
| 42 | + num_quotes += 1; |
| 43 | + } else if ch == '\\' { |
| 44 | + num_backslashes += 1; |
| 45 | + } |
| 46 | + } |
| 47 | + |
| 48 | + // Allocate output String. |
| 49 | + let mut result_size = input.len() + num_quotes + 3; // two quotes, plus a NUL |
| 50 | + if !as_ident && num_backslashes > 0 { |
| 51 | + result_size += num_backslashes + 2; |
| 52 | + } |
| 53 | + |
| 54 | + let mut output = String::with_capacity(result_size); |
| 55 | + |
| 56 | + // If we are escaping a literal that contains backslashes, we use |
| 57 | + // the escape string syntax so that the result is correct under |
| 58 | + // either value of standard_conforming_strings. We also emit a |
| 59 | + // leading space in this case, to guard against the possibility |
| 60 | + // that the result might be interpolated immediately following an |
| 61 | + // identifier. |
| 62 | + if !as_ident && num_backslashes > 0 { |
| 63 | + output.push(' '); |
| 64 | + output.push('E'); |
| 65 | + } |
| 66 | + |
| 67 | + // Opening quote. |
| 68 | + output.push(quote_char); |
| 69 | + |
| 70 | + // Use fast path if possible. |
| 71 | + // |
| 72 | + // We've already verified that the input string is well-formed in |
| 73 | + // the current encoding. If it contains no quotes and, in the |
| 74 | + // case of literal-escaping, no backslashes, then we can just copy |
| 75 | + // it directly to the output buffer, adding the necessary quotes. |
| 76 | + // |
| 77 | + // If not, we must rescan the input and process each character |
| 78 | + // individually. |
| 79 | + if num_quotes == 0 && (num_backslashes == 0 || as_ident) { |
| 80 | + output.push_str(input); |
| 81 | + } else { |
| 82 | + for ch in input.chars() { |
| 83 | + if ch == quote_char || (!as_ident && ch == '\\') { |
| 84 | + output.push(ch); |
| 85 | + } |
| 86 | + output.push(ch); |
| 87 | + } |
| 88 | + } |
| 89 | + |
| 90 | + output.push(quote_char); |
| 91 | + |
| 92 | + output |
| 93 | +} |
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