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NULL
#' @export
#' @rdname sqlParseVariables
sqlCommentSpec <- function(start, end, endRequired) {
list(start = start, end = end, endRequired = endRequired)
}
#' @export
#' @rdname sqlParseVariables
sqlQuoteSpec <- function(start, end, escape = "", doubleEscape = TRUE) {
list(start = start, end = end, escape = escape, doubleEscape = doubleEscape)
}
#' @export
#' @rdname sqlParseVariables
#' @param sql SQL to parse (a character string)
#' @param quotes A list of `QuoteSpec` calls defining the quoting
#' specification.
#' @param comments A list of `CommentSpec` calls defining the commenting
#' specification.
sqlParseVariablesImpl <- function(sql, quotes, comments) {
str_to_vec <- function(s) strsplit(s, "", fixed = TRUE)[[1L]]
sql_arr <- c(str_to_vec(as.character(sql)), " ")
# characters valid in variable names
var_chars <- c(LETTERS, letters, 0:9, "_")
# return values
var_pos_start <- integer()
var_pos_end <- integer()
# internal helper variables
quote_spec_offset <- 0L
comment_spec_offset <- 0L
sql_variable_start <- 0L
# prepare comments & quotes for quicker comparisions
for (c in seq_along(comments)) {
comments[[c]][["start"]] <- str_to_vec(comments[[c]][["start"]])
comments[[c]][["end"]] <- str_to_vec(comments[[c]][["end"]])
}
for (q in seq_along(quotes)) {
quotes[[q]][["hasEscape"]] <- nchar(quotes[[q]][["escape"]]) > 0L
}
state <- "default"
i <- 0L
while (i < length(sql_arr)) {
i <- i + 1L
switch(
state,
default = {
# variable
if (sql_arr[[i]] == "?") {
sql_variable_start <- i
state <- "variable"
next
}
# starting quoted area
for (q in seq_along(quotes)) {
if (identical(sql_arr[[i]], quotes[[q]][["start"]])) {
quote_spec_offset <- q
state <- "quote"
break
}
}
# we can abort here if the state has changed
if (state != "default") {
next
}
# starting comment
for (c in seq_along(comments)) {
comment_start_arr <- comments[[c]][["start"]]
comment_start_length <- length(comment_start_arr)
if (
identical(
sql_arr[i:(i + comment_start_length - 1L)],
comment_start_arr
)
) {
comment_spec_offset <- c
i <- i + comment_start_length
state <- "comment"
break
}
}
},
variable = {
if (!(sql_arr[[i]] %in% var_chars)) {
# append current variable offsets to return vectors
var_pos_start <- c(var_pos_start, sql_variable_start)
# we have already read too much, go back
i <- i - 1L
var_pos_end <- c(var_pos_end, i)
state <- "default"
}
},
quote = {
# if we see backslash-like escapes, ignore next character
if (
quotes[[quote_spec_offset]][["hasEscape"]] &&
identical(sql_arr[[i]], quotes[[quote_spec_offset]][[3]])
) {
i <- i + 1L
next
}
# end quoted area
if (identical(sql_arr[[i]], quotes[[quote_spec_offset]][["end"]])) {
quote_spec_offset <- 0L
state <- "default"
}
},
comment = {
# end commented area
comment_end_arr <- comments[[comment_spec_offset]][["end"]]
comment_end_length <- length(comment_end_arr)
if (
identical(sql_arr[i:(i + comment_end_length - 1L)], comment_end_arr)
) {
i <- i + (comment_end_length - 1)
comment_spec_offset <- 0L
state <- "default"
}
}
) # </switch>
} # </while>
if (quote_spec_offset > 0L) {
stop("Unterminated literal")
}
if (
comment_spec_offset > 0L && comments[[comment_spec_offset]][["endRequired"]]
) {
stop("Unterminated comment")
}
list(start = var_pos_start, end = var_pos_end)
}
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